De Rossi facing Roma fine
The 29-year-old was sent off for punching Stefano Mauri, as Roma fell to a 3-2 defeat to their great rivals.
As a result of his dismissal, Italian coach Cesare Prandelli has left the midfielder out of the Azzurri squad.
"The club's position is clear. In these cases, we will fine the player based on how long they are suspended for," Baldini told Football Italia.
"I spoke to Daniele before the game and he wanted to do well.
"He was really determined to achieve a positive result and seeing Lazio fight back to go in front must have brought this reaction out of him."
Baldini was also quick to play down an alleged rift between Zdenek Zeman and Miralem Pjanic, following speculation that the midfielder shouted insults towards the coach after he scored.
"Pjanic was not angry at Zeman. This squad is made up of over 22 players and everyone has to compete for a place.
"The lad clarified the situation and there is nothing to discuss.
"It is normal that someone has to be left out and that they will react to it, as they care about the cause.
"Pjanic is an exemplary professional and we will leave it at that."
Lazio coach Vladimir Petkovic, meanwhile, was singing in the rain on Sunday following his side's victory.
In sodden conditions at the Stadio Olimpico, the 49-year-old could only praise his players after seeing them overturn Roma's early lead.
Petkovic suggested it was his players ability to adapt throughout the match that saw them gain a vital three points.
"I don't have anyone in particular to dedicate this derby win to," said Petkovic.
"I dedicate it to the club that believed in me and definitely to my players who proved tonight that they are worth something and they can compete at top level.
"I hope everything will continue like this. Let's rest now and then we'll prepare for next game.
"The team proved today they really deserved this victory, also from a mental point of view," Petkovic added.
"I think we were better and we were good at adapting ourselves to different rhythms and situations throughout the game, we adapted our play to what was needed."