Guardiola is immensely complaining about Rodri missing the game and that the referee sent him off anyway. Can't recall the foul right now, but I am sure Manchester City has someone on the bench who is just good enough to play instead of Rodri. 
I don't know where you saw Pep complaining about Rodri missing the game, i've watched all Pep's press conferences this season and after the Nottingham Forest game, Pep was actually angry at Rodri (and not the ref) for losing his head and getting sent off. Pep has been asked countless times if Rodri would be a big miss for City, and he accepted that he would be greatly missed, and of course that is true, Rodri is the best defensive midfielder in the world and City have missed him since he has been suspended and they will miss him on Sunday, but Pep hasn't be complaining, instead he said they will find a solution, which i'm pretty sure they will.It is a big game on Sunday, and it is almost impossible to predict, Rodri is a big miss and i think Saka might also miss the game due to injury. City have a good run of defeating Arsenal, thus i expect it to continue.
I just don't understand, why Rodri banned also from playing in the EFL Cup before, when Manchester City played against Newcastle yesterday in the EFL Cup match. Although in fact, Rodri got a red card only in the Premier League, then at least Rodri should still be able to play in the match against Newcastle in the EFL Cup yesterday. But in fact, that Rodri was still banned from playing also in the EFL Cup . After all, Rodri basically only got a red card in the Premier League and of course, Rodri only be banned for playing in the Premier League and not for other matches outside the Premier League. But yes, considering Rodri got a red card when playing against Nottingham, I think Rodri shouldn't play with a hard game like that, because he only played against Nottingham which is certainly not a difficult opponent for Manchester City.