McDermott was axed earlier on Monday with Reading four points adrift of safety after suffering their fourth successive defeat against fellow strugglers Aston Villa on Saturday.
Roberts admits he was shocked by the news and he paid tribute to the job McDermott has done at the Madejski Stadium after guiding them to promotion to the Premier League last season.
"Well I am saddened," Roberts told Sky Sports News. "I hadn't heard anything about it I just found out earlier and as in most situations players are probably one of last people to find out about these things.
"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 in football it's a result business and I am sure he will say that as much as anybody else but as a player I am disappointed and it is a sad day for us."
Roberts believes McDermott deserves praise for what he has done at the club during his time in charge.
"It is always tough in these situations we are not party to the discussions had between the manager and whoever else," added Roberts.
"All we can do is just try and perform as best we can on the pitch and I think the performances we have given up to this point to allow Reading to be in Premier League and be in the position we are now have been over and above what people would have expected.
"In the Premier League certainly we would have liked to have done better and liked to have been out of relegation zone but from my point of view I think it is an important time to look back and feel the success what Brian has achieved, what this group of players have achieved with the club and take stock of what a great situation Reading find themselves in.
"At the moment we have got nine games to go there is an opportunity for us to remain in the premier league and we've absolutely done better than people would have expected certainly with the promotion and of course everyone wrote us off at the start of the season.
"With nine games to go we still have an opportunity to achieve Premier League survival.
"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 because that is the goal and even Brian McDermott would say the same thing."
A host of names including Nigel Adkins and Paolo Di Canio have been linked with replacing McDermott, but Roberts wouldn't be drawn on who he wanted to get the job.
"It's not a decision we are party to," Roberts continued. "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."