Some things that might make it less frustrating for you, sort of in order:
* Unplug your pad if that's an option, so the game will show you the proper keybinds.
* While hanging, you should be able to look around with the mouse on most pipes, so you can at least get an idea of what's next to you. Typically pressing A -> jump or D -> jump will make you switch pipes easily, but there are a couple of pipes that are annoying to jump between. For long jumps off buildings at pipes, you may want to use slow motion (R) shortly before the jump.
* I still miss rolls while landing sometimes. It should be pure timing that gets easier with practice, though. I think if you press it at the last second it may fail, so pressing it slightly earlier could help.
* For cops, make sure you turn the difficulty to easy. This will make combat easier and bullets should hurt you less, which may let you just ignore the cops and run behind obstacles in a lot of cases. If you feel you have to fight, one easy tactic to taking down isolated cops is to run, slide, and kick them in the groin. They'll double over, and you can use A or D to circle behind them. Just AFTER they stand back up, press disarm to immediately break their neck and take the gun. If you feel it's impossible to isolate a guard and you HAVE to take him out, try running, slide kicking, then backing up and running away. They should die after a few slide kicks. Also you can occasionally use slow motion (R?) to help you with the disarm timing, if you want to do the face-to-face disarm.
* You can keep in motion a lot of the time, once you become more familiar with the level layout. But yes, the first time through the game, it may be hard to avoid cops since you're not sure where you're going. I assume you're playing it with the red highlighting on. That SHOULD help give you hints in several places so you know where to keep running and jumping.
