im building an l-shaped addition to connection my house to my carport, half of addition is between house and carport the other half is behind carport, trying to figure out how to do the roof on this addition and tie it in to the two roofs

Complex intersections of surfaces, like some sheet metal duct transitions, can be solved by using descriptive geometry, but the easy way is to build 1/20 scale cardboard mockups of the roofs and cut and paste the pieces to fit.

Take your drawing to a local truss company. They will need to know all the measurements including pitch of both roofs, height of garage compared to house, width of garage, width of the house and overhang and seat cuts of both roofs For seat cut, give them the distance between the top of the wall on the outside and the bottom of the roof sheeting.