What Roles Can Vel'koz Play?

Nope. Just mid and support. Most champs only cover 1-2 roles. Although you could take him as a bot lane carry if you really wanted to in this meta.

Off the rift he has a very lucrative career in adult entertainment... but yeah. On Rift he's basically bot lane or mid.

You can always take him to that dumpster that welcomes any champion. Also knows as top lane. If you really want to. Nothing horrible will happen.

Vel’Koz can go top but he’s only good against Teemo and juggernauts like Darius, Garen, and Nasus; champions that cannot safetly touch him.

Just those two. Although you could probably get away with him top lane in incredibly rare cases where he has the matchup advantage, he's still going to get ass-blasted by any competent jungler that rolls through top lane, so it's not a great idea.

velkoz :

magic damage, true damage, spell caster, squishy, slow movement, skill shots, displacement

everything but jungle. why not jungle? velkoz doesnt have sustain through spell vamp, lifesteal, etc.

He can also play tentacle hentai with Illaoi.

Anything can be played anywhere with the right match-up.

If you really enjoy him, play him in any lane. Try to scrutinize your match-ups though, and pick him when you feel comfortable.