“I really really want the club to succeed,” the 22-year-old told Sky Sports.
“From growing up watching them at Belle Vue and then at Keepmoat (Stadium), I’ve kind of grown up with it and I’ve felt the passion and to have the opportunity to potentially make a difference in the club is huge for me.
“What’s in it for me? Financially nothing. It’s just to hopefully be a part of something great and I think we can really do that at Doncaster.
“It’s a footballing town, Doncaster, there is no doubt about that, and it will be great to feel that for myself.”
Tomlinson said he had a particular interest in the youth set-up at the club, which was relegated from the second-tier Championship last month, and bringing back ticket deals for families.
The purchase included the Doncaster Rugby League FC and the charitable Foundation.
“During the interim period between now and the 18th July, the new owners of Doncaster Rovers will be working with Paul Dickov to help secure his transfer targets,” a statement on the club website said.
“All parties sincerely wish both John Ryan and Louis Tomlinson the best of luck for the future and are looking forward to seeing the club progress under their stewardship.”
Tomlinson and Ryan had set up a crowdfunding campaign to raise two million pounds ($3.39 million)for the club, with the Tomlinson Ryan Trust putting in a “six-figure sum” to start.
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The group was formed on British reality singing television show “The X Factor” in 2010 and has a huge following in the United States.
(Reporting by Josh Reich; editing by Clare Lovell)