The Town boss, who has brought in Jordan Flores on loan from Wigan Athletic this week to compensate for the almost-completed sale to Portsmouth of Dion Donohue, says they’re looking at a multitude of candidates to improve the squad.
And they’re currently running the rule over a pair of trialists - who may feature in match action next week.
“We’ve had two (trialists) in,” said the Scot.
“They’ve been in training for a few days, we’re potentially looking at playing a game next week for non-starters on Saturday and some trialists.
“We’re continually trying to improve the squad and make it better.”
That hunt for new players will be boosted by the news of a windfall in the region of £70k from the Donohue sale.
But that cash seems likely to go into wages, rather than transfer fees.
“I don’t think we’d pay fees, there’s too many good players out there that are available - whether it be on loan or on a free, to get out of clubs, or don’t have clubs,” said Caldwell.
“I don’t think there will be fees but we do have the potential now to bring players in.”
Former Chesterfield man Roberts left Chesterfield two years ago, joining Paul Cook at Portsmouth.
The 33-year-old added last season’s League Two title to the one he captured with Chesterfield in 2013/14.
He scored 10 times in 42 matches for Pompey last term.
Caldwell admits he’s an option they’ve given some thought to.
“We’re looking at lots of players,” said the boss.
“He is one we have looked at, as we’ve looked at hundreds of players.
“We’re ready to act and if that player becomes available, within our budget and will improve us as squad then we’ll do everything we can to get him in.
“But it is difficult, we have other clubs trying to get players, you have agents and it’s difficult to get deals done.
“So far I think we’ve done extremely well and if we continue to work the way we have then we’ll continue to bring good players in.”