Roberts hasn't played since diving into first base during a May 16 game in Boston. Collins examined him for the first time on May 24 and recommended that Roberts be shut down for two weeks.
Roberts had complained of dizziness and other symptoms that he related to motion sickness.
Justin Duchscherer, who still hasn't pitched for the Orioles this season, is scheduled to throw five innings Tuesday in an extended spring training game.
Duchscherer went four innings in his last outing. He was hit in the stomach by a line drive in the first, but continued to pitch.
The Orioles will decide whether Duchscherer is ready for an injury rehab assignment after Tuesday's start.
First baseman Derrek Lee won't be officially activated from the disabled list today until he takes batting practice, but it's considered a formality. Lee batted four times last night at Double-A Bowie and didn't experience any discomfort in his left oblique.
Lee is batting fifth tonight to relieve some of the pressure on him in his first game back. And Adam Jones deserves to take some swings in the third slot.
Showalter will need a fifth starter for Tuesday night's game against Oakland at Camden Yards, and he said all three options remain in play. He's including Chris Jakubauskas, who pitched two innings in relief last night. The Orioles also could give the start to Alfredo Simon or dip down into the minors.
Triple-A Norfolk's Mitch Atkins started Thursday and would be working on normal rest. He's 1-1 with a 3.52 ERA in three starts, with six earned runs (11 total), 17 hits, six walks and 13 strikeouts in 15 1/3 innings.
Chris Tillman started Wednesday for the Tides, but he hasn't been in the minors for the required 10 days.
The Orioles need a fifth starter only twice this month, so the easiest solution would be to use one of their current relievers. However, they have an open spot on their 40-man roster and could purchase a pitcher's contract without needing to make a corresponding move.
For the Blue Jays:
Yunel Escobar SS
Corey Patterson LF
Jose Bautista RF
Adam Lind DH
Juan Rivera 1B
J.P. Arecibia C
Aaron Hill 2B
Rajai Davis CF
Mike McCoy 3B
Ricky Romero LHP