Roberts, who was diagnosed with a small herniated disc in his lower back a few weeks ago, said he didn't have any pain when bending over to field or while taking swings off the tee.
"It's a matter of I haven't done a whole lot of sprinting on the ground, I haven't done a ton of rotational stuff [with hitting]," Roberts said. "So those are the two things we are just gradually working back into it."
Roberts did everything but hit live on the field on Tuesday, including getting some work in the cage with hitting coach Terry Crowley, and Roberts was optimistic in his assessment.
"I'm not very far behind," Roberts said.
Roberts' even-keel attitude is partially due to the fact that he doesn't usually hit much in the offseason. So starting a week or so behind the rest of the team isn't a cause for concern.
"He's ready to go," said manager Dave Trembley, who touched base with Roberts on Tuesday morning. "He will be fine."
The 32-year-old Roberts began experiencing nagging back spasms during his offseason workouts at the Athletes' Performance Institute in Arizona, and was originally misdiagnosed with kidney stones before doctors found the herniated disc a week later.
On Monday, Roberts said his back was already feeling better than it was a few weeks ago, and right now his goal is just to be ready for the team's Opening Day game on April 6.
Chris Tillman is also progressing well, and Trembley said as long as he is cleared by head athletic trainer Richard Bancells, the right-hander will throw a side session on Wednesday.
Tillman missed his last scheduled side session earlier in the week due to back spasms attributed to falling asleep on a couch in an awkward position.
Although it was just a minor setback, the 21-year-old was relieved that he felt good during a 10-minute catch session and fielding drills Tuesday.
"It's not all the way gone yet, but I am very relieved," Tillman said. "We will see how it feels off the mound. I'm not going to go 100 percent obviously ... no reason to rush right now."
Tillman won't participate in throwing live batting practice on Wednesday, and neither will right-hander Brad Bergesen. Bergesen, who is rehabbing a strained right shoulder capsule, came out of his flat-ground session on Tuesday with a good report from Trembley and should get on the mound sometime this week.
Brittany Ghiroli is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.