Play some single player on easy and find the ranges where you can comfortably hit the semi-dormant bots, using different weapons, fire modes and stances. Concentrate on one or two classes per session, or total confusion will be the likely result.
In close quarters twitch and a cool head are more important than accuracy. A friend of mine has significantly lower accuracy than I have, but he owns me almost every time, and has a k/d ratio more than 3 times better than mine. Strafe, crouch, move around (don't go prone unless using an LMG, you get way too slow) and fire many short bursts at his centre of mass (easier to hit) or his face (1-shot kill with any weapon except pistols or SMG:s, that take 2).
Fiddle around with this against "tougher" bots, the easy ones are too slow to improve your reflexes.
Someone correct me if I'm wrong, but I think the roll is just a cool animation when going prone from a strafe or sideways jump. That is, it's nothing to learn and you are probably doing it already (you crowdpleaser, you:)). The first-person view is not affected, it doesn't roll 360 degrees.