Manchester-born Tunnicliffe first came up through the youth ranks at Stockport County and once had trials at Anfield with Liverpool.
"We feel James is an excellent addition to the squad," Rovers manager Paul Trollope told the club's website.
He added: "He is a highly-rated young defender who attracted a lot of interest from clubs over the summer once it became clear that Brighton would listen to offers.
"It is a year long loan with no recall but we see it as a loan to start, with the potential of a permanent deal to follow."
Tunnicliffe made 41 league appearances for Stockport before signing a three-year deal at Brighton in June, 2009. However he fell out of favour after Gus Poyet took over as manager from Russell Slade.
"I can't wait to get started," Tunnicliffe said. "I thought that Rovers did well last season after an impressive start and they finished in a strong position."
Rovers face Greenock Morton on Saturday followed by Partick Thistle on 20 July.
Source: BBC Sport
Source: BBC Sport