Flat roof advice

I appreciate things are hard to explain without pics but here goes. I have a square house with an attached square garage (just say it is the same size as the house) but this is set forward of the house by around 2 metres. I am building a small extension to the rear of the garage so back of house and garage will all now be one line. I am putting a flat roof onto this extension (the garage is pitched) I so effectively I am building two walls at an L shape. a few questions
1) my garage internal roof height is quite high and if I put new joists in for extension and attached them to existing garage wall plate it would make my extension roof seem very high and look odd. I aim to attach a trimmer along width of garage but on the wall vertically but a brick courses or so below the existing garage wall plate. Would this be acceptable considering the new trimmer plate will be at near top of wall?
2 Rafters, The one closest to the house, is this actually attached to the house as well? Or does it come in a bit so just goes between garage and new outside wall? I will be using joist hangers on the new trimmer but obviously won't be able to use one on the joist closest to house if attached to house.
3) likewise the other end furthest away from the house, the 2m span, does a joist sit on the outside cavity as well or do I put one on a wall plate in the internal cavity and build a ladder to span outside cavity so I have something to attach facia board etc to attach too
Sorry for the multitude of questions and I am sure there will be more, thanks in advance

You have to have pics.. Sorry

Sorry not built fully yet so pictures won't really help, I will try to upload some if I know how to, to give you an idea but anyone any thoughts of what I have written if they understand what I mean, the main one at the moment is question 3, the rafter that runs parralel to the 2m span.

So you want to know:

1. Wall plate on garage wall. Bolt it on at say 600mm centres. Even though its only got a cours or so of brickwork above, I would think its ok, a flat roof doesnt have much load.

2. Depends how you want to finish you flat roof fascia, but if its going to have an external gutter, the plate can sit on the outside skin, then build oit with fascia detail as needed. If you want a big overhang then you need to overhang the joists and do a ladder on the side thats parallel to the joists.

Thanks for the reply, re question 3, no gutter that side as gutter will be along the 5m length, this side will have facia flat against brickwork so yes could run rafter on outer wall but how would this fit into trimmer plate? If I used joist hangers, (like I will be )there has to be a bit of trimmer plate beyond last rafter for joist hangers to attach too, so trimmer plate would stick out beyond wall, which obviously can't happen, what's the best way of fitting that last rafter to trimmer plate which would suit BC? Hope that makes sense