Have you read the books? Because if not, then know this: Movie!Ron is not Canon!Ron. Canon!Ron is NOT afraid. The chess scene in PS/SS (included in the movie), he faces his fear of spiders for Hermione in CoS and willingly goes into the chamber. In PoA, he's the one (NOT Hermione) who stands up and goes, "If you want Harry, you'll have to go through us first," to Siruis; broken leg and all and believing that Sirius is a murderer! So Ron is NOT a coward. Otherwise he would not have been placed in Gryffindor.