Who is the most talented F1 driver in the current roster?

You're fooling yourself if you say anybody except Alonso. Unfortunetly it's a very competative sport, which relies heavily on the car. Lewis is good but he lacks maturity. Vettel is boosted by a very good car. Schumacher is past his prime.

The only guy anywhere near Alonso is Button, but he doesn't seem to have the head for qualifying.

di Resta, and then Hamilton. They have both beaten Vettel in lower formulas where the cars were identical.

Sebastian Vettel

Fernando Alonso! :D He is a double world champion and pushes his current car a lot further than Massa can so with the same car and engine and all that he would win easy!

Seb Vettel. Then probably Hamilton. Followed by Alonso/Rosberg.

Michael Schumacher! Don't forget that when he was the absolute champion, all the rest, that people mentioned here, were just annoying kids that were running whole laps behind him.

Jenson Button definitely

The way he handles that car is incredible.

Lewis Hamilton as long as he can control his occasional lunges.