The opportunity for Roberts came along when the Red Sox lost Will Middlebrooks for at least the next couple of weeks with a right calf strain.
"I'm very excited," said Roberts. "I just feel very blessed to be here and a part of this organization. I've played against the Red Sox for a few years and to actually put on a uniform, it gives you a different feel, so I'm very excited about that. Hopefully I can add anything they need. I've been fortunate over the years to play everywhere and a lot of positions. Hopefully my versatility can play a part in anything they need."
What the Red Sox will need from Roberts at the outset is to start at third base against left-handed pitching, meaning he will likely get the nod for Tuesday and Wednesday's games against Martin Perez and Robbie Ross.
For his career, Roberts is a .245 hitter with 46 homers, 169 RBIs and a slash line of .321/.392/.713. But he's better against southpaws, hitting .266 with a line of .341/.444/.785.
With Middlebrooks out, he will platoon with Jonathan Herrera.
"We felt like we needed to add another right-handed bat, third-base capable and some versatility to the defensive side," said Red Sox manager John Farrell. "We're probably looking at a little bit of a platoon-type situation at third base in the short run. Ryan's here because we didn't feel like the time was right for Garin Cecchini. Even though he's put up some good at-bats, there's still development to be had defensively. More importantly, the right-handed bat just helps balance out our lineup."
Roberts is fine with any role after getting a taste of unemployment.
"If I had to relate it best, I would say it was like the Bud Light commercial where they pick the guy up and they just take him on a wild, crazy night and journey," said Roberts. "That's kind of been my deal here. It's been a crazy journey. It's been an experience that I've never dealt with before and it's long days. The days sometimes go by really fast. My days went by really slow.
"It's been a nice ride, a learning experience. And hopefully I just try to take every day with a sound mind, calmness, and trusting that God is going to put me in a position on the right team that I could excel with and hopefully that time period that I was down and I just wasn't with the team, hopefully that will be information I can give [others] to use in that situation later on down the road."
To make room for Roberts on the 25-man roster, the Red Sox optioned infielder Brock Holt to Triple-A Pawtucket. To clear space on the 40-man roster, right-hander Steven Wright was transferred to the 60-day disabled list.
Roberts, 33, has spent parts of the last eight Major League seasons with the Blue Jays (2006-07), Rangers (2008), D-backs (2009-12) and Rays (2012-13). He appeared in 18 Cactus League games with the Cubs this spring.
Roberts has hit .245 with 204 runs, 71 doubles, four triples, 46 home runs, 169 RBIs, 163 walks and 35 stolen bases across 510 Major League games.
Roberts has played 217 games at third in his career, while also spending time at second base (197 games), left field (36), first base (three), shortstop (one) and right field (one).
Over four stints with the Rays last season, Roberts hit .247 with six doubles, five homers and 17 RBIs in 60 games.
Holt, who was recalled to Boston on Sunday, did not appear in the Red Sox's game against the Brewers. Wright has been on the DL since March 27 (retroactive to March 21) while recovering from right sports hernia surgery.