Roberts sparked a nationwide debate when he announced he would refuse to wear a campaign shirt during the warm-up after what he perceived to be a lack of action about racism in football.
Roberts' gesture was criticised by Manchester United manager Sir Alex Ferguson, though more than 30 players from eight Premier League clubs chose to withdraw their support for the Kick It Out awareness drive at the weekend.
Roberts' Reading team-mates Garath McCleary and Jem Karacan removed their shirts during the pre-match routine, while United's Rio Ferdinand and brother, Anton, who plays for QPR, were among those who followed suit.
And McDermott says he stands by Roberts' decision: "I spoke with Jason about it, and he was very clear in his views," he explained. "I supported him 100%, he had his reasons. You'll speak to him about them and, like I say, I support him 100%."
Roberts made the decision because he feels Kick It Out have not been strident enough in relation to recent race abuse incidents like the ones involving John Terry and Liverpool striker Luis Suarez.
Last week the 34-year-old striker also called for any player racially abused during a match to walk off the pitch in reaction to the ugly scenes that marred the England Under 21s match against Serbia Under 21s.
McDermott added: "When you consider what's gone on this week in Serbia with Danny Rose, it's incredible, I've never seen anything like that and I've been in football all my life.
"I wrote to Danny Rose this week because I thought the way he conducted himself was first class and he looks like a top guy.
"Hopefully we can put these issues to bed because they don't belong in football, or in society.
"It's an emotive subject, and rightly so. People feel very strongly, and I can only speak for Jason and my players, Jason feels very, very strongly about it. I back him 100%."
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