On June 1, 2010, Ullström was signed by the New York Islanders to a three-year entry-level contract.[2] He scored his first career point on November 29, 2011, assisting on Brian Rolston's 3rd period goal against the Buffalo Sabres in a 2-1 win. On December 6, Ullström scored his first NHL goal against Mathieu Garon of the Tampa Bay Lightning.[3]
On June 18, 2013, Lokomotiv Yaroslavl signed Ullström to a contract for the 2013–14 season.[4] Scoring just 3 goals in 18 games with Lokomotiv, Ullström transferred to HC Lev Praha for the remainder of the campaign. Establishing a scoring presence within Praha, he helped the club advance to the Gagarin Cup finals.
On June 25, 2014, Ullström opted to remain in the KHL, signing for his third club, Severstal Cherepovets on a two-year deal.[5]
On May 15, 2018, Ullström returned to the NHL after five seasons in Europe by signing a one-year, two-way contract with the Arizona Coyotes.[6] He began the 2018–19 season on the injured reserve and upon returning to health was assigned by the Coyotes to AHL affiliate, the Tucson Roadrunners for the duration of his contract. He recorded 10 goals and 23 points in 29 games for the Roadrunners.
Unable to break into the NHL, Ullström returned to Europe, signing a contract with Latvian based club, Dinamo Riga of the KHL, on May 30, 2019.[7]
In the 2022–23 season, he was signed to a one-year contract with the Schwenninger Wild Wings of the Deutsche Eishockey Liga (DEL). He featured in only 17 regular season games with the Wild Wings, contributing with 5 points. Unable to help Schwenninger advance to the post-season, it was announced Ramage would leave the club at the conclusion of his contract on March 9, 2022.[9]