The 35-year-old, who won the Championship title with the Royals in 2011-12, hasn't played for over a year due to a persistent hip injury and remains doubtful about his future despite undergoing a range of treatment including surgery in March.
"It's been really frustrating," he told Goals on Sunday. "I've had an operation, steroid injections, time abroad - we've done everything we possibly can do and we just haven't been able to get it to a point where I'm fit enough to play yet.
"I've had six or seven opportunities to try and come back and we've not made it through two or three training sessions.
"It's really frustrating. I've never really been injured before but I think when you go through something like this at my age, you start to really question how much longer you can go on. But it certainly makes you realise how lucky you've been."
The forward, who counts Bristol Rovers, Wigan, West Brom and Blackburn among his former clubs, admitted that he is still unable to run due to the pain his injury causes him.
"I'm actually not able to get out of a jog. The surgeon went in, he shaved some bone away and re-attached some cartilage; it was micro-fractured. It was quite a big issue.
"I should have been back in four to five months but it has been over a year now, so it's a frustration for everyone. But as a professional football player all you want to do is play football and when you've never been injured before you realise just what some people have been through.
"Two weeks ago I would have said 'yes' [I will get through it] but after my recent breakdown I'm a little bit concerned but we'll go back to the surgeon and see what he says.
"In the end you can only try to come back a number of times before you realise it is not going to happen; the last breakdown was a couple of weeks ago. I couldn't get through a training session after training for two or three weeks.
"So I'll go back to the surgeon because I'm going to need a life after football and I'm sure I'm going to need a new hip anyway. If I could play I would, but at the moment it's restrictive."
Roberts signed for Reading in January 2012 and hit the ground running, scoring four times in an eight-match unbeaten run before the club clinched promotion to the Premier League - a feat he describes as one of the highlights of his career.
"The frustrating thing is that, physically, I still feel like I can do it. When I was out there on the pitch I had a great run of form and we won promotion - something that no-one could have seen when I arrived there.
"So it was a fantastic time in my career; the Premier League season obviously wasn't as good as we would have liked, but still it was a great achievement for a side that ability-wise should have been in and around mid-table of the Championship.
"So to achieve what we did and to get to the Premier League was, in my opinion, one of the biggest achievements of my career."
Reading currently sit seventh in the Championship after a Kaspars Gorkss header secured a 1-0 victory over Watford on Saturday and Roberts believes that under manager Nigel Adkins the Royals have as good a chance - if not better - of securing promotion this season.
"We're certainly a better collection of individuals [than in 2011-12] - we're better players - but if you are a team coming down people look at you and maybe look at the way you play and try to nullify you in different ways.
"You are a scalp now whereas we weren't when we got promoted. Now people are dealing with us in a different way; a new manager has come in with different ideas. He wants us to keep the ball more, rest on the ball, dominate possession.
"It's a different way of playing, so I think it has taken a little bit of time to get there. Nevertheless we are in and around the play-offs and once you are in that position in the Championship, anything can happen.
"It has not gone as smoothly as we would have liked but while we are in the race, anything is possible."