This fight is canonical it takes place in "Dragon Ball Z: The World's Strongest" between ep 39 and 40 so not far but still. I suppose they can take similar dmg but yes Naruto can regenerate. Also short range kamehameha isn't suicide because we seen alot of them just disintegrate target and fly away, but Mafūba is but i don't think he will try seal Naruto. If we assume chakra and ki are same then Naruto will be out of fuel later than Roshi. I'm still sure its fair fight and victory wont be easy.