The Mariners had been going with an extra reliever since sending left fielder Norichika Aoki down to Tacoma two weeks ago.
"We wanted to get the bullpen back to normal and get the extra position player back," manager Scott Servais said. "We thought it was a chance to bring Robertson in here and play him tonight against [Astros starter Dallas] Keuchel. We'll kind of see where we go coming out of the break, I'm not quite sure where we'll go there yet. But it gives him a chance to come in here and hopefully help us out."
Robertson, who batted eighth and played in left field on Tuesday, has hit .274 with 28 RBIs and six stolen bases in 107 Major League games. He finished 0-for-2 against the Astros.
"The first time up with a new team is always special," Robertson said before the game. "This will be my third different one. But it's equally as special. You spend some time at Triple-A with some guys that have never made it. You try to give them all the information that you can. And then when you get the call, you feel it all over again. I remember the first time. It's always like the first time."
Robertson has been around enough to have faced Keuchel several times in his career.
"He's a Cy Young winner and he's also a great guy, too," Robertson said. "I've played against him since 2010. I knew Keuchel before a lot of people here did. It's a familiar face. It doesn't make it as difficult as everyone makes it seem. He's a competitor and when the lights come on at 7 o'clock you don't really think about what they have, you just think about competing. "
Rollins ran into a numbers game in the bullpen, but the 2015 Rule 5 Draft pickup continues to impress. He's pitched in four games for Seattle over two stints with the big league club this season and has yet to allow a run in four innings.
To make room for Robertson on the 40-man roster, right-hander Adrian Sampson was transferred to the 60-day disabled list as he recovers from a right flexor bundle strain.
• How much has Tom Wilhelmsen impressed since being re-acquired from the Rangers? Servais said if closer Steve Cishek has to work several games in a row, he wouldn't hesitate to go to Wilhelmsen to close out a game in his place.
• Right-handed reliever Nick Vincent started playing catch Monday at Safeco Field as he works his way back from a mid-back strain that landed him on the DL last week, but Servais said he's just beginning to throw again and isn't sure on potential rehab assignments.
• Felix Hernandez remains on target to throw a three-inning simulated game prior to Wednesday's series finale at Minute Maid Park as he ramps up his rehab from the strained right calf that has sidelined him for five weeks.
• The Mariners acquired outfielder Ryan Strausborger in a trade from the Rangers in exchange for a 2016 international slot compensation. The 28-year-old hit .200 in 21 games with Texas last year and .288 with four homers and 16 RBIs in 45 games for Triple-A Round Rock this season. He'll report to Triple-A Tacoma.