Walker was eligible to receive a $221 million supermax extension over five seasons, but the Hornets offered him just under $160 million.
Williams has spent the last five seasons in Charlotte. He averaged 10.1 points and 5.4 rebounds in 75 games in 2018-19.
“Most of the (starting) point guards in this league make between $15 million and $35 million (per season,)” Hornets GM Mitch Kupchak said.
"This was an extremely tough decision, and I hope people on both sides will take that the right way," Walker wrote.
Kemba Walker is eyeing success in the playoffs after agreeing to sign with the Boston Celtics.
Boston is the landing spot for the three-time NBA All-Star.
Rozier, 25, averaged 9.0 points, 3.9 rebounds and 2.9 assists per game for the Celtics in 2018-19.
Walker reportedly agreed to a four-year maximum contract worth $141 million with Boston, which he is expected to sign Sunday.
Boston is the rumored landing spot for the three-time NBA All-Star.