Before either he or Elan got Giant Axe to the Face'd, 3E action economy says Roy could've done two of three things: stand up, attack, pick up sword. Add in that choosing to leave out "stand up" would've resulted in I-forget-what kind of crazy penalties to the attack, I think he made the right call. (And, as others have pointed out, he is leaning over to pick up the sword in the last panel.)
Plus, if the universe conspires to let you uppercut a frost giant, I think that's something you just gotta go for.