The Royals were beaten 2-1 at home by Aston Villa on Saturday to remain 19th on the table with McDermott copping the wrath of owner Anton Zingarevich despite being named the Premier League Manager of the Month in January.
"Well I am saddened," veteran striker 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."
He added: "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."