I play bass fairly melodically, and I know some more rhythmical guitarists- myself being one of them. I think that instrument "roles" shouldn't be as rigid as they seem to be, bassists shouldn't have to just play "root notes with some fills", they should be able to play whatever the hell they want, and similarly, guitarists shouldn't be limited to "widdly bits" or "chord strumming".
I listen to prog/tech metal though,