I am building a 20' X 24' carport and was trying to decide if a ridge beam / board was necessary, or could i simply use gussets to connect the roof rafters. I'd like to avoid using a 24' beam if possible. The design is using 4 x 4 posts with 2 x 6 rim joist around. The roofing will be a metal roof on purlins (no sheathing). So, gussets or ridge beam (or does it matter)?
Gussets wouldn't replace a ridge beam (which is different from a ridge board). You'd need a truss design with collar or rafter ties.
If you don't have a ridge beam (which actually carries the load from the upper half of the rafters), you need rafter ties, which run across from wall to wall. Gussets don't provide the sort of bracing that rafter ties would.