Real's all-time top scorer Ronaldo missed their first two league games of the season and their European Super Cup triumph over Sevilla while recovering from a knee injury he sustained playing in the Euro 2016 final for Portugal.
He told reporters on Thursday, however, that he would face Osasuna, declaring: "I'm ready".
Spanish newspaper Marca reported earlier in the week that the forward, who scored 35 goals in 36 league games last season, will play 60 minutes against Osasuna as coach Zinedine Zidane eases him back into action.
Benzema has been recovering from a hip injury sustained towards the end of last season, but is expected to start alongside Ronaldo and Gareth Bale, allowing Zidane to field his first choice 'BBC' attack for the first time this season.
Real barely noticed the absence of their two forwards as they eased to a 3-0 win over Real Sociedad in their opening game thanks to goals by Bale and youngster Marco Asensio, although they then laboured to a 2-1 win over Celta Vigo.
"I'm excited about our game with Osasuna, they will make things difficult for us but it'll be fantastic because we'll have our full team available," Bale told reporters on Wednesday.
Champions Barcelona and Las Palmas are the only other teams in the league to have won two games this season.
Barca will be boosted in attack this weekend by the return of Brazil forward Neymar, who missed the start of the season to play at the Olympics in Rio de Janeiro, leading his country to their first soccer gold medal.
Neymar also scored the winning goal in Brazil's 2-1 World Cup qualifier win over Colombia on Tuesday.
Luis Enrique's side, however, could be without Lionel Messi after he returned early from international duty suffering with discomfort in his groin, the same injury he was carrying when he travelled to his home country to play against Uruguay.
Messi's absence could free up a place in the starting lineup for new signing Paco Alcacer, who joined Barcelona from Valencia for 30 million euros ($33.74 million) at the end of last month.
"If the coach decides I can play, a footballer always has to be ready for everything, especially at a club like Barcelona," Alcacer said on Thursday at his presentation.
Atletico Madrid travel to Celta Vigo in Saturday's early game while league leaders Las Palmas, who are top on goal difference, travel to Sevilla.
(Reporting by Richard Martin; Editing by Toby Davis)
