The player can perform anywhere in the back four and it casts further doubt over the future of rumoured Iron transfer target Dave Mulligan.
"We have been after James for quite a while and feel he is one of the best in his position at this level," said boss Dave Penney.
"We knew we would have to offer a transfer fee but believe it will be worth it."
He joins Ipswich's Kevin Horlock and Yeovil's Adam Lockwood in signing for Rovers this week.