United's reward for overcoming neighbours Manchester City 3-2 on Sunday was a meeting with their bitter rivals from Anfield.
Rooney, whose two goals helped United to victory at the Etihad Stadium, wrote on his Twitter account: "What a draw for next round. Another big game. Can't wait for it already."
Fellow United striker Michael Owen, who scored for Liverpool against United in a fourth-round tie back in 1999, added on the social networking site: "And people talk about United always getting lucky cup draws!!! Couldn't get much tougher. What a game to look forward to."
The tie will be played on the weekend of January 28 and 29, and will be the first meeting of the sides since the controversial clash in October when Liverpool forward Luis Suarez racially abused United defender Patrice Evra. Liverpool accepted an eight-match ban for the Uruguayan over the incident earlier this month.
United have won the competition 11 times, while Kenny Dalglish's men have triumphed on seven occasions.
