patio cover

I am looking to build a cover over an existing concrete patio. the slab is 10 ft deep and 12 ft long. I am going to tie rafters to a ledger attached to the facia and rest them on a beam between 2 6x6 post set 11 ft apart. rafters will need to span 8 1/2 ft and will be on 16 in centers. my question is size of beam and rafters. I live in Texas , so there is no snow load to consider. It will have 5/8 plywood roof with roll roofing. thanks for your advice.