Structural Mass Street

I need someone to design a structural beam to carry a flat roof load. The roof is 20' wide by 25' Long. The rafters are 2x10 16" OC free-spanning the width of 20 from North to South . The 2x10's are about 16 feet long and they over lap in the middle to span the 20' distance. The rafters are sagging in the middle from the weight of the roof. The roof consists of 1x10 nailed perpendicular on top of the rafters. There is a layer of 3/4 plywood on top of the 1'x10's. There is a layer of asphalt rolled roofing on top of the plywood. There is then a rubber membrane covering the rolled roofing. I plan on spraying 2" of Spray closed cell foam on top of the rubber membrane with a latex coating on top of the foam to seal the roof. The Rafters run North and South and sit on top of the North wall and the South Wall The North wall is a 2x4 knee wall framed on top of an 8" wide foundation stem wall that sticks up 8" above the floor. The South wall consists of a 2x4 Knee wall that sits on top of an 8" Hollow block wall with a 16"x 32" column in the East and West Corners respectively. The East end of the building contains an 8'x 18' wide overhead door. with a 2x10 header that sits above the door and a 2x4 knee wall extending above the header to the roof. Overall height from floor to bottom of rafter is 160". The West end of the Building is a 2x4 wood knee wall 55" tall sitting on top of a 2x8 wood wall that is 8' tall and sits on top of a foundation stem wall that is 8" tall by 8" wide. Overall height from floor to bottom of rafter is 158". I am looking to span 2 beams under the rafters running perpendicular (East To West). First Beam would would be located 72" from the North wall running parallel to the North wall. The second beam would be located 72" from the South wall running parallel to the South wall. These 2 beams would be supported by 4 LVL's running underneath the beams and tied to the North Wall and the South Wall. On the North Wall, the LVL's Will be tied to the existing 2x4 framing with additional Framing added under the LVL to carry to the load to the 8" stem wall. The LVL's will be supported on the South wall in the same manner. LVL will be tied to existing 2x4 framing with additional framing underneath the LVL to transfer the load from the LVL to the 8" block wall. I need the 2 steel beams designed along with the 4 LVL's designed and specified. I'm not opposed to another design idea. if you think 4 LVL's is overkill, 3 would be ok.