Getting in to a snaproll is easy. It's the getting out that's the fun part.

From level flight, full up elevator, full rudder and full aileron in the same direction all at once.

(Note, many planes will snap with just elevator and rudder (and some will do it with just elevator or just rudder), but many sport planes need the ailerons to help. It's "more correct" to use just rudder and elevator, but easier to control when you add in ailerons. Some planes will snaproll with just elevator and ailerons (often on final approach. Perhapse you've seen this happen, usually accompanied by a pilot yelling "I've been hit" and followed by the creation of a smoking crater?)).

Anyway, given the control inputs, one of three things will happen.

1) One wing stalls, the other doesn't (or doesn't as much), and you get a snaproll. Most planes recover just by centering the sticks. The recovery often isn't instant, some planes continue to roll more than others (my cap would do 3/4 of a roll after releasing the controls. 2 snaps were easy, but 1 snap was really hard to get the exit upright. In any event the hard part is exiting upright. You're first few snaps will likely leave you inverted or sideways or who-knows-where. Most common crash after a snaproll is not figureing out which way it's really going after exiting, and doing the wrong thing.

2) The wings don't stall, and you get a really sloppy corkscrewing roll. If this happens, you need to increase controls throws (esp rudder and elevator) or move the CG back, or both.

3) You rip the wings or tail off. Snaps are rather violent in nature, and stress the airframe. If you do it going really fast, it's not out of the question that some part of the airframe might decide it would be happier on it's own. This is actually rare, but not unheard of. So, keep the entry speed and throttle fairly low at first. Some planes like more or less power to snap, and some planes handle it better than others. It's not unheard of for a plane to snap better at low speed and high throttle, meaning that you throttle down, drop airspeed, then hit the power, elevator, rudder, and ailerons at more or less the same time. You probibly won't need to do that, however.

Have fun!