What are roof rafter?
2 by 4s that hold the plywood onto the roof are call rafters.
They are not usually 2" x 4"'s but are more likely to be 2" x 6"'s and on larger homes near high roof pitches are 2" x8"'s.
The group at the top and are nailed into a ridge board.
Roof rafter can be used to form a regular pitched roof with gables on the ends, or hip roofs which adjectives 4 sides are on the same pitch and near are no gable ends.
Some framers now use Truss joist " T J I 's vs. conventional lumber for rafter. The TJI's come in long length and are straighter than dimensional lumber.
Rafters are used in "Stick framing".
Trusses enjoy replaced a lot of stick framing contained by the last 20 yrs.
Answers: generally, these are the 2 x 8"s that you see surrounded by your attic that support the actual roof and its shingles.