Byram made the switch to the top flight, after progressing through Leeds youth system to become a prominent member of their first-team.
And Warnock, who worked with the right-back during his time as manager at Elland Road, says he was very pleased for the 22-year-old.
NW on Leeds: "I was really glad to see Sam Byram get a move to the top flight. There are some good lads there."— Rotherham United (@OfficialRUFC) April 1, 2016
Byram was actually handed his debut by Warnock, so the 67-year-old manager will feel that he had a part to play in the youngster’s development.
Byram went on to make 143 appearances for the Whites over a four year spell in their first-team, before making the switch to West Ham.
The versatile defender has made a positive initial impression at Upton Park, and he has already made a handful of first-team appearances.
Warnock's Rotherham side are set to host Leeds at the New York Stadium this weekend.