Many, many years ago my father and I ran a fly fishing school in Devon, England on the river Torridge. The pool we used to teach Spey casting on was almost ideal. It was wide enough to throw a full line, shallow and gentle enough to wade to the other side and teach casting from both banks and had a nice high bank from which we used to video casters under tuition. The only thing that was wrong with it was that there was not a lot of current. The caster would stand on the left bank (river flowing from right to left) cast a Single Spey across the pool and then have to wait quite sometime for the current to wash the line back to the dangle. This got frustrating and so I used to use two Roll casts to get the line back downstream (there were too many trees lining the pool to do an overhead cast). The first Roll cast was to get the line in the right area and the second to straighten it out. Over the course of time I started to speed the two roll casts up, merging them into one fluid movement and thus became the Snake Roll. My father saw me doing this cast and recognised it as a cast in its own right with a number of fishing applications and so we came to name it. Being a young kid in those days I wanted to call it the Sausage Roll, but my father's wisdom prevailed and we called it the Snake Roll.
Since starting to teach it as a cast on its own merits (in the early 80's) I have seen the same cast done by many good casters and frequently heard it called by other names. This just goes to show that there is nothing new in the casting world. When you believe you have created a brand new cast, you are not alone. Someone else has probably been doing it for years!
The Snake Roll as a fishing cast is used in exactly the same situation as the Double Spey - with a downstream wind, right hand up on the right bank and left hand up on the left bank. So, if it is used in the same situation as the double spey why learn it? In truth you don't need to know the Snake roll if you can do the Double Spey. However, casting is a skill, and, like any other skill, there is immense satisfaction in doing something well, to the best of one's ability and, in particular, being able to do everything possible. In truth, the Snake Roll changes direction faster than the Double Spey, which equates to more time with your fly in the water and, therefore more fish. The snake roll takes about 4/7 of the time of a double spey. In other words, in the time it takes you to do 40 double speys, you could do 70 snake rolls (if you were only casting, not fishing or anything). It also makes a lot less disturbance on the water than the Double Spey and, finally, some casters find it easier to learn than the Double Spey.
Don't think that this cast is limited to the two handed rod. This is far from the truth. I use the snake roll constantly with the single-handed rod when trout fishing for a fast change of direction when dry fly fishing, or when swinging nymphs and spiders. It is even more useful when saltwater fishing on the flats when change of direction and speed is of the utmost and likewise when lake fishing and you need to cover a moving fish fastů nothing is faster and more efficient than the snake roll.
So, how do you do it?
The snake roll can change angles through a wide range from a zero degree angle change to a 180 degree angle change, but initially it is easiest to learn with a 90 degree angle change. So, (assuming you are a right handed caster) start with the fly line somewhere to the right hand side of your body and choose a target about 90 degrees to the left of your starting point.
Start the rod tip pointing directly down the fly line, but slightly raised to the level of your hat peak. Draw a lower case 'e' (counter clockwise) with the rod tip - big and bold, but finish the 'e' by lifting the rod tip up to 1 o'clock. The speed of the 'e' should be along these line; Slow, Medium, Fast. In other words, draw the flat, horizontal part slowly, speed up to a medium pace on the first half of the circular motion and then accelerate on the lower half of the circular motion and up to 1 o'clock with the rod behind you and directly opposite where you want to cast the fly. This acceleration throws the belly/D loop behind you to load the rod. Remember, the faster this final acceleration is, the bigger the D-loop will be. When tight to obstructions not so much power should be used in this acceleration.
All the time you are drawing the 'e' shape try and keep your rod tip held away from and make the movement more from your shoulder than your wrist. A useful analogy here is to imagine you have a piece of chalk jammed into the tip of the rod and that the chalk is resting on a brick wall. The brick wall runs at ninety degrees to your target, off your downstream shoulder. You want to draw the 'e' and the lift up to 1 o'clock on the wall and be careful not to pull the chalk away from the wall whilst you are doing it.
What should happen, if you get the 'e' shape and speed right, is that the fly line, leader and fly will jump out of the water from the dangle and land about ten feet to your right hand side, dead straight and pointing towards your target.
Once you have finished the back stroke and formed the D-loop behind the rod you should have rocked all your weight on the back foot (the right foot). It is then a simple matter of finishing off with a forward cast. On this note, however, remember that timing is vital. The back stroke should make the entire fly line lift completely out of the water and re-land parallel to the target and it is imperative hat the forward cast starts the moment the first piece of fly line or leader touches the water. This is what I call a "Splash & Go" cast. This means there is no pause for the anchor to settle. The moment that the first piece of fly line touches the water the forward stroke must start and must drive close to and parallel to the anchor (without crossing it).
Initially casters should practice this cast in two parts, working on getting the back stroke right before worrying about timing and forward stroke. To get it right, the fly and line must jump out the water from the dangle and land dead straight in front of you and parallel to the target. As you get more accomplished with the backstroke, start to watch where the tip of the fly line lands. To start with it will be somewhere in front of you - maybe 20 feet or so. As you get better and more control of this stage of the cast, you should try and get the tip of the line to land directly downstream of you - in your wading wake, though still facing the target. This will give you the biggest D-loop and load and the most efficient of all casts. However, be warned, when you are tight to restrictions this big D-loop can be a problem and snag behind you, so a true master of this (and all spey casts) can adjust the size of the D-loop behind according to the amount of space there is.
Practice with different shapes, sizes and speeds of 'e' to see what results you get. Remember that "flat is good" and the better you get the flatter and more compressed your 'e' should be. This will give you a higher line speed behind that loads the rod deeper and more aggressively and results in a more efficient and deadly snake roll.