Home Studio design question: angled roof

Hi guys, I've been looking around on these forums for quite some time now and found some very valuable information up until now. I've looked trough quite some drawings and plans, but I didn't find one that matches my situation though :) So here I go: my "studio" is located on the attic and has the following measurements: Width: 3.5 Meters Length: 8.5 Meters Height: 3.7 Meters There is one thing though: the roof is angled from the floor up to the top (highest point 3.7 meters) making some sort of triangle. On one side of the roof there is a window that is approx 0.90X1.25 Meters that has the same angle as the roof has. One side of the walls is painted concrete, the other walls are 1/2" plasterboard on a timber frame (actually both sides of the frame have plasterboard on it, there is nothing in between). The roofs are made of particle board, covered with 'standard' rockwool roof insulation (sorry to be kind of vague on this but I don't check under my roof every day). The floor is concrete, covered with (thin) carpet. Sorry I couldn't deliver any pictures/drawings, I'm at work at the moment ;) My aim is to provide at least a decent mix spot. I do record vocals/guitars in the same room, so its desirable to treat the room in such a way that also recording can be done with a reasonable result. Loudness is not the first priority since the only loud thing I record is an electric guitar which i could set at a 'decent' level. Furthermore, at first I would like to spend about € 500, so $700. I understand this is a very tight budget and I might do more later on, but at this point this is what I'd like to start with. The main thing that I don't know what to deal with is the angled roof and the effect it has on the acoustics, just some info on this would really help me out. I hope I didn't miss anything important and of course thanks for looking ;) Edit: I've added 2 sketchUps to give a general idea of the layout. Nothing fancy

then add a "corner" absorber in the peak of the ceiling, a porous absorber on the back ceiling and a couple of absorbers on each side of the desk.

Thanks very much for the advice, I can work with that. I do have another question though, suppose i'd turn the desk around with the monitors pointing towards the roof, what would change? I guess the absorber in the notch still stands, as well as the absorbers on the sides of the desk, but what about those absorbers behind the monitors? I've attached a sketch to give an idea of what this would look like. Also, (very important i think) there is a book case on the right side sitting from behind the desk and a closet on the left side. I could get trid of the closet on the left side if this would improve things. Which of both options do you think would be best?

from my perspective, its looks pretty much the same either way. my only other concern is the book case itself. anyway to trade that in for a much lower unit ot two? this way you don't have something that is likely to add a close and reflective surface on one side. if you could use a couple of lower units on each side it would be less likely to be a problem plus you could use them as keyboard stands ;-)

Thanks again Glenn for the quick response ;) I'm affraid im stuck with that book case, it major and there's no other place we could put it.. man I need a bigger house :) I'm going to use my suberb DIY skills here, so I looked up all the plans and stuff. I planned on using these plans for the regular absorbers: http://www.johnlsayers.com/phpBB2/viewtopic.php?t=4581 and I think I should be able to use the same concept for the roof. However, a porous absorber puzzles me.. would that be the same thing with different rockwool/insulation in it? Thanks again for all the patience ;)

porous absorber = rockwool/rigid fiberglass = broadband