A media panel voted for the winner, while players are also required to have made a minimum of nine Vodacom URC appearances to qualify.
"It is a huge honour to get this award, I am so grateful to everyone who has supported me this season," said Roos.
"My family is a great source of strength and pride for me and everyone involved in the DHL Stormers set-up has been amazing as well. I am so proud to play for this team and our incredible fans every week."
The 22-year-old Roos has had a stand-out campaign for the DHL Stormers, proving himself a destructive ball carrier with more successful carries (126) and defenders beaten (49) than any other player in the competition over the 18 rounds.
Roos carried his regular-season form into the play-offs by putting in a Vodacom URC Man of the Match performance against Edinburgh Rugby in the quarter-final last weekend.
He was earlier this week also named in the Vodacom URC Dream Team along with four of his DHL Stormers colleagues.
Vodacom URC Award Winners List 2021-22
Tackle Machine: Alan O’Connor (Ulster)
Turnover King: Jac Morgan (Ospreys)
Gilbert Golden Boot: Gareth Anscombe (Ospreys)
Top Try Scorer: Leolin Zas (DHL Stormers)
Ironman: Ruan Nortje (Vodacom Bulls)
Next-Gen Player of the Season: Evan Roos (DHL Stormers)