First of all, I'd recommend you play the hotel mission again. Your health is too low for the rooftops mission. The hotel mission is not that hard. Start killing the guys on the lobby, then kill the guy behind the counter and also the guy on sailor clothes on the dining room on the left hand side of the reception.
Then, take the service stairs on the hallway located on the right-hand side of the reception and go really careful here, always ducking. You should be able to surprise the guy waiting for you behind a coffee table by approaching from the side (he's expecting you to come from the main stairs). After that, use the main stairs to climb all the way up, embushing every hood that tries to blast you with pump-actions. A good trick is to stay cool and wait for them to come downstairs after you, then start shooting as soon as they are on your radar. If they take too long, try to carefully show yourself a little so that they are aware of your presence. Repeat this procedure until you knock them all out, find the w*h*o*r*e on one of the rooms on the 3rd floor, kill the manager's body guard, kill the manager, blow the hotel.
If you need extra health, there's a medicine cabin inside the small room behind the reception.
For the rooftops mission, I have a few tricks: first, do all the way upstairs using the fire escape. When you're up there, go to the rooftop on the left side and just ambush the cops that go up after you. You should kill them all without losing any health with this method. Pick their guns and continue your path towards the church. Careful when you find small passage near some chimneys. That place is crowded with cops! A good strategy is to show urself and climb back where you came from, shooting'em from a distance. Alwways be careful because sometime's you think they're all waste, but one of them can still be hiding behind a wall or something.
Pay special attention to the the cops on the higher roof and also one cop that is all alone after the chimneys. That guy has a rifle that can hit you pretty bad.
After that, next mission, the Priest :-) Good luck!
[Edited by thiagoene, 5/14/2010 2:49:09 PM]