Caley Thistle attacker Connor Bell is searching for a new club after talks over a new contract broke down.
Englishman Bell netted seven goals in 35 appearances after joining on a one-year contract last summer following a spell with Swiss outfit Servette. The Newcastle-born player previously played for Wrexham, Rhyl and Rotherham.
With tighter budget constraints as a result of a second successive season in the Championship however, Robertson, who has already signed Dumbarton wide player Tom Walsh, says he cannot allocate the funding required to retain 21-year-old Bell.
Robertson said: “The club has another reduced budget because the parachute payment has gone down.
“We have looked at players and at this moment in time Connor is in a position where he’s battling against players in the team who have already got contracts.
“We have got Aaron Doran back fully fit in that area, and we’ve got Tom Walsh in that area as well now.
“Connor had a decent season for us last year and his agent wants a better deal for him, but we are not in a position to offer that. That’s where we are.”
Walsh is one of three new arrivals so far, along with Queen of the South right back Shaun Rooney and Hearts midfielder Angus Beith, and Robertson reckons he is close to completing his transfer business for the summer.
He added: “If we can add another couple of players that would be about it, I would think.
“We have tried to get our business done early which is not always easy. You don’t always know who is available, and sometimes you go back to players who are not available at the moment who will be available nearer the deadline.
“It’s a tricky act. There wasn’t any time last year, simple as that. We signed a lot of players quickly and some worked out, some did not.
“As most managers will tell you, most of the squad work starts in February or March to try and see who you want to get at your club, and who wants to come to the club.
“It’s difficult because a lot of players you are interested in have agents who want to see what else is available in the market. It’s in the lap of the gods but you’ve just got to use your contacts and try to sell the club, and show people what you are after, what you want to achieve and where you want to go.”