Wales drew 1-1 with Northern Ireland on Thursday without key players Gareth Bale and Aaron Ramsey.
The match also saw Chris Coleman's side adopt a four-man defence instead of their usual five, and there could be more experiments against Ukraine on Monday.
"We want to make sure that we have options up our sleeves," said Roberts.
"We want to try things otherwise perhaps we'd be criticised for only having a plan A and no plan B, so we are working on that. And that takes time."
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Wales play Ukraine in Kiev on Monday evening in their penultimate friendly match before the Euro 2016 finals.
They face Sweden in Stokholm on 5 June before kicking off their finals campaign against Slovakia in Bordeaux on 11 June.
"We'll pick a side to win the game against Ukraine, but at the same time it's an opportunity for one or two players and we still want to try one or two things," he added.
"Because if we don't do it now we won't have an opportunity to do and we've got a few things that we want to look at naturally that gives people an opportunity."
Manager Coleman also hinted he will make changes for the match in Kiev, which will again see him without his star duo Bale and Ramsey.
"We had a few bodies missing [against Ireland] but you learn about other players," he said.
"It gave us a chance to look a bit closer at players like Lloyd Isgrove and Danny Ward. It's nice to give them a bit of experience.
"Sometimes it's about more than the result."
Assistant manager Osian Roberts says Wales have been working hard on trying to develop a plan B for Euro 2016.