Drawings for a new roof and loft conversion on some garages

I have a garage block which needs re-roofing. Currently the building has a roof of concrete tiles and has a 45 degree pitch. The rafters also need replacing. I would like to reroof the building to a slightly higher pitch of 50 degrees and clad with oak shingles to reduce the weight and avoid cross bracing if possible to make the loft space usable. I would like to convert the attic area into a small flat at a later stage. I would also like to repeat a gable end to effect a cross shape of the roof as a whole. I am looking for detailed drawings to be able to get a builder to quote