The German midfielder joined the Blues on a season-long loan on transfer deadline day in September 2025, with the deal always set to convert into a permanent transfer provided Everton retained their Premier League status - a condition met when David Moyes's side secured survival before the campaign's end.
Röhl has now signed a three-year contract at Goodison Park, running to June 2029, for a fee reported at around £18m.
It capped a first season that started slowly, with the 23-year-old needing time to settle before establishing himself in Moyes's midfield. He made 20 appearances in all competitions and scored his first goal for the club against Sunderland in May, in the final home game of the campaign.
The Germany Under-21 international arrives with a reputation as a versatile operator capable of playing through the middle or further forward, and Moyes is expected to lean on him more heavily as first-choice competition for places in central midfield next season.
Röhl's first year on Merseyside was not without its setbacks. An early injury interrupted his integration into the squad, and it took a strong performance against Manchester City before he began to earn more regular starts under Moyes.
"We're really pleased to bring Merlin to Everton," Moyes said when the midfielder first arrived. "He's a Germany Under-21 international who will add different qualities to our existing midfield options. He's an exciting prospect who we've followed at the Club for some time, and we're all looking forward to working with him as we continue to build a squad and team at Everton."
Röhl progressed through the youth ranks at SV Babelsberg 03 and FC Ingolstadt before signing for Freiburg in 2022, where he spent three years in the Bundesliga prior to his move to England.
Off the pitch, he has settled quickly into life at the club, striking up a friendship with Everton great Leighton Baines and speaking openly about his affection for the city and its supporters.
Röhl becomes the third permanent addition to Everton's squad for the 2026/27 campaign, following Hayden Hackney's move from Middlesbrough and the permanent signing of Tyrique George.
With his long-term future resolved, Moyes will look to further reinforcements as he shapes his squad for a first full season since Everton's move to their new stadium.