Blue attacking up the pitch; B1 does the roll ball
B2 passes to B3 (who's running onto the ball)
B3 passes to B4 (who is aiming inside R4), and R3 "loops" round behind R4.
If the defenders don't react we have a 3 on 2 (draw the opposite number and pass to put B5 free down the wing.
Variation: (B2 should always run this, and B4 can decide who to pass to)
R3 and R4 react to the loop and push across to cover the loop by B3.
B4 dummies to B3 and passes inside to B2 (who did the initial pass from the roll ball and ran back to be behind the ball), coming on a late line inside R3