The 35-year-old forward believes the now former Royals boss was a "victim of his own success", and is adamant he should be proud of what he achieved with the club during his time at the Madejski Stadium.
But despite his sadness at the decision, Roberts has urged his team-mates to focus on the task at hand and ensure they remained in the top flight for another season.
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"I am saddened because he has been absolutely fantastic for us, been fantastic for me personally and for the club and I think he's been a victim of his own success in some ways.
"I am sure he is going to be disappointed but, as you know, football is a results business, and I am sure he will say that too. But as a player I am disappointed and it is a sad day for us."
"We've absolutely done better than people would have expected, with the promotion and, of course, everyone wrote us off at the start of the season.
"We have got nine games to go and there is an opportunity for us to remain in the Premier League."
The former Wigan striker refused to comment on who would might take over the Royals, with Paolo Di Canio, Nigel Adkins and Alex McLeish all linked to the the post.
However, Roberts did want to thank McDermott for all his work at the club, and urged the team to continue the work he began.
"As a player it is just for me to place on record my thanks to Brian McDermott on what he has achieved, and whatever goes from here on in we need to work hard and keep Reading in the Premier League," he added.
"It's not a decision we are party to. All we can do is concentrate on what we do on the pitch and on the training ground and do our best for Reading - I don't think anyone would say anything different.
"What we need to do is make sure we leave Reading in a good position. I think Brian McDermott has done that and I think we owe it to the club and owe it to Brian as much as anyone, to do the best we can."