I'd have him playing either flank Zat for now just as that's how he'd fit in the team (not saying he's ready to be a guaranteed starter - he isn't imo).
But to me he's neither a winger nor a 10. He's the classic 'inside forward'.
Really, we only play with inside forwards if we go 3 at the back, with a four across the middle and then the 'two' either side of the main striker (Ross excelled in an inside forward role last season).
I think though, towards the end of the season, supposing we stick with four at the back, then I'd like to see him played centrally even if it's just for spells in a game. His pace and trickery will be really useful in that role I think.