The centre-half has had a procedure to help cure a persistent groin problem.
Manager Garry Monk said Roberts had a similar issue to Harlee Dean, who underwent an operation for a hernia three weeks ago.
Roberts came in for Dean for Blues final two matches of the campaign and performed admirably in both.
But he also has been playing and training through the pain of injury and a visit to theatre to go under the knife was required.
Monk said: "He was carrying a similar type of injury to Harlee - and he has probably been carrying it for a similar time as well.
"He just needed it done, like Harlee has, it's a very small one and both should be fine for pre-season.
"With the squad the way we had it this season we needed everyone and they all managed to make it to the last week or couple of weeks of the season.
"That's testament to the fitness work that has been done and also the players themselves, the mentality they have had.
"I was keen to praise Marc when he was playing because like the others he had put himself on the line.
"That's what I said to him at full-time (at Reading): 'I have been there myself, especially as a centre-half'.
"The reason I say 'as a centre-half' is because as a centre-half generally you have to play 90 minutes.
"Very rarely will a centre-half be substituted. Other positions if you are carrying injuries you can make substitutions.
"I understood the ask of him for those last two games playing that position so I was very, very pleased with him and for him."
Roberts has had to play second fiddle to the Dean - Michael Morrison pairing for the majority of this campaign.
His first league start came in December at Blackburn Rovers but unfortunately he injured his calf after just nine minutes and then spent a lengthy spell on the sidelines.
But with Dean absent for the last two games and Morrison ruled out due to an ankle injury, Roberts stepped into the breach for the draws against Wigan Athletic and Reading.
Alongside Wes Harding in a new-look centre-half combination, like his partner he was excellent in both games.
Monk added: "It has been a little bit difficult for Marc as well, obviously Harlee and Morro had the shirt and hadn't really done anything to lose that shirt.
"Between the three of them it has been difficult, either two of those could easily play and keep the shirt regularly.
"Then he got his opportunity to play at Blackburn and unfortunately he got injured.
"There is one hundred per cent a Championship defender in there so I am looking forward to him coming back strong this pre-season and giving himself the best opportunity to fill that shirt."