The Castleford-born full-back/stand-off, 20, was on Wakefield Trinity's books as a youngster but made his professional bow with Warrington Wolves.
He switched to Hull KR last year and has made nine appearances this term.
However, with the club's squad now approaching full-strength, he will struggle for game-time over the next four weeks and been allowed to head out by coach Tony Smith.
Full-back Adam Quinlan has returned from an ACL and Danny McGuire is back in the side tomorrow night after missing the last three games with a calf strain.
Dagger - who is contracted at KR until the end of 2020 - will instead go to Championship Featherstone in search of greater involvement.
He is likely to come straight into their plans for Sunday's game at Halifax.