The 23-year-old joins the Serie A giants for a fee believed to be around £15m plus bonuses according to Goal.com, and now can't wait to join up with his new teammates.
However, he was made to wait as negotiations dragged on while the two clubs attempted to come to an agreement over his valuation.
"I'm really happy I'm finally here," he told reporters. "The negotiations went on a bit too long, but I'm finally a Roma player."
The Dutchman has been capped 18 times by the national team, and joins a whole host of new faces at the Stadio Olimpico this summer.