Rodri was sent off immediately after halftime following a clash with Morgan Gibbs-White.
Guardiola said: "He has done it. He has apologised. [He said] Sorry.
"Rodri has to control his emotions. I can get a yellow card but Rodri cannot get a red.
"I don't play, the players in the pitch have to control their emotions."
On the home support, Guardiola said after the 2-0 win: "You can lie to one person but not almost 60,000 people.
"It's impossible. They see we are not lazy, they see we do everything to defend a result from the difficulties we had in the second half.
"The spectators are involved in that and that's why they can give more energy when they are tired."