Joining a roof to an outside roof

Hi. I am planning on building a bike shed outside at the end of my garage. The roof will join onto timber posts that will have side walling. The roof would probably be sheet metal or similar with felt, but it would be joined to a brick wall - can anyone advise on how I join the roof to the wall and ensure the join is properly water tight and the water effectively runs off?
The more details the better - materials needed, any treatments, best practice, etc!
Thanks
Cofty

Go to Wickes - they have good stuff for that type of diy roofing and decent leaflets to guide you Also Google cavity trays of yeovil

Flash - aha