Ronaldo scored two goals as Brazil beat Paraguay 2-0 to advance to the semifinals of the America Cup.
Brazil, the defending World Cup champion, will face Peru on Wednesday in the tropical city of Santa Cruz.
In one of the bigger upsets in South American soccer, Peru eliminated two-time World Cup champion Argentina 2-1 on Saturday.
Three Argentina players were expelled, and Marcelo Gallardo missed a penalty kick 3 minutes into the second half.
In the other semifinal, Bolivia will play Mexico on Thursday at La Paz.
Mexico also advanced Sunday, beating Ecuador 4-3 on penalty kicks after the teams played to a 1-1 tie at Cochabamba.