FC Copenhagen A
right-back, Roerslev progressed through the
academy at
F.C. Copenhagen and made his senior debut as a second-half substitute for
Frederik Bay in a
Danish Cup third round match versus
Jammerbugt FC on 26 October 2016. He capped a dream debut with a goal in the 6–1 victory. Roerslev made four further appearances during the
2016–17 season and signed a new four-year contract in May 2017. He worked to improve his one-on-one defending with experienced right-back
Tom Høgli. Down the pecking order at the
Parken Stadium, Roerslev appeared sparingly during the
2017–18 and
2018–19 seasons. but made few appearances for either club, Roerslev departed FC Copenhagen in August 2019, Roerslev broke into the first team squad in October 2019 and by March 2020, after 10 appearances, his performances led to him signing a new four-year contract and promotion into the first team squad. Roerslev ended the
2019–20 season with 14 appearances. He returned to match play in early January 2021 and after a number of substitute cameos, an injury to his mentor,
Henrik Dalsgaard, allowed him to break into the
starting lineup in early April. He held onto his place until the end of the regular season and through the
playoffs, a change in formation to
3-5-2 saw Roerslev begin the
2021–22 season behind stand-in right
wing back Sergi Canós in the pecking order. Approaching the midway point of the season, mounting injuries in the central defensive positions saw Roerslev deployed in a right
centre back role. He finished the 2021–22 season with 26 appearances and one goal, scored with the winner in a 2–1 Premier League victory over
Aston Villa on 2 January 2022. injuries to both players led to Roerslev assuming the starting right back role in mid-October 2022. He ended the campaign with a season-high 38 appearances and one goal, scored in a 2–2 draw with
Chelsea on 2 March 2024. Roerslev was again the only recognised right back available and competed for the position with stand-ins Kristoffer Ajer and
Sepp van den Berg. He made 23 appearances prior to joining
Bundesliga club
VfL Wolfsburg on loan for the remainder of the season on 27 January 2025. Roerslev made just seven appearances during the remainder of the season, predominantly as a substitute. With former loan right back
Michael Kayode signed permanently and dual-sided Aaron Hickey fit again, Roerslev remained an unused substitute during the opening match of the
2025–26 season. Roerslev ended his Brentford career on 146 appearances and two goals. He made his first appearance for the club on 23 August in a 2–1 home defeat against
Stoke City. ==International career==