Connor Essam's move to Leyton Orient is complete after the Sky Bet League 2 side agreed a fee with non-league Dover.
Midfielder Danny Guthrie has become Blackburn's third signing of the summer.
Rotherham have signed Blackburn defender Jack O'Connell on a youth loan.
The England youth international, 18, who can play centre-back or left-back, will stay at New York until January 5 and could make his debut in Saturday's League Two clash at Exeter.
The news comes on the same day as Josh Morris returns to Rovers from Steve Evans' Millers after his loan spell was cut short following a knee injury.