Ronaldo, the Nassr captain, headed home Ghislain Konan's cross three minutes from time on Thursday night for the Riyadh side to draw 1-1 with Egypt’s Zamalek in their final Group C match.
Staring at defeat in Taif, Nassr were on the brink of an exit, but Ronaldo’s goal ensured they moved above Zamalek into second in the table to progress to the quarter-finals.
Runners-up in last season’s Saudi Pro League, Nassr will now face Morocco’s Raja Casablanca, the defending champions, in their last-eight encounter on Sunday.
Speaking after the match, Ronaldo said: “The match was difficult today, but we were able to achieve the important thing, which is qualifying.
"We will gradually improve, and the atmosphere within the team is very nice."
On Thursday, Nassr gave a debut to latest signing Mane, whose move from Bayern Munich was confirmed only two days back.
The former Liverpool forward, who joins at the club fellow summer recruits Marcelo Brozovic, Seko Fofana and Alex Telles, was brought on at the beginning of the second half.
Keen to immediately make an impact, Mane went close to cancelling out Zizo’s 54th-minute penalty, but sent a close-range effort narrowly off target.
Posting on Instagram after the game, the Senegalese forward commented on a picture of him and Ronaldo embracing, saying: "Congrats on your goal big man. On to the next round. Thanks Al Nassr fans, the support was amazing."
Earlier on Thursday, UAE side Al Wahda lost 1-0 to Raja, but still had done enough to advance to the knockouts. Pitso Mosimane’s men face Riyadh’s Al Shabab on Sunday – Shabab pipped Nassr to the top of Group C – while the tie of the quarter-finals is undoubtedly the all-Saudi clash between domestic champions Al Ittihad and Al Hilal, on Saturday.
Meanwhile, Qatar’s Al Sadd face Iraqi club Al Shorta in the other last-eight encounter, also on Saturday.