"Ronaldo gives us a sense of security and confidence," said Allegri of the beaten finalist in two of the last four editions of the elite European competition, AFP reported.
"The team is essentially the same as last season. We've grown, become faster in playing the ball, but then of course, there is Cristiano Ronaldo.
"This team is constantly improving – they're passing and putting play together more quickly."
Ronaldo – who joined Juventus last summer from Real Madrid – is targeting a sixth Champions League title to add to his four with the Spanish team and one with Manchester United.
The Italian team is looking for its third European title and first since 1995.
Last season Bianconeri exited in the quarterfinals to Ronaldo's Real Madrid.
The 33-year-old played a key role against Valencia providing the assist on 59 minutes which Croatian Mario Mandzukic tapped in for his third goal in as many matches.
Juventus had needed just a point to ensure qualification.
its win combined with Manchester United's late 1-0 win over Young Boys at Old Trafford means Valencia crashes out of the competition.
Allegri's side will now have to wait to see whether it tops Group H when it plays its final group game mid-December in Bern against Young Boys.
"You can see how united we are including the forwards," said Juventus captain Giorgio Chiellini.
"All three of them – Ronaldo, Mandzukic and Dybala, really put themselves about today. If we scrap like that, with the skill we have in the side, it makes everything much easier.
"We have to turn the page now – we'll start thinking about the Champions League again in February. We must focus on Serie A because we have a tough month ahead," added the defender as the league leaders target an eighth consecutive domestic title.
"The match was decided by great play by Cristiano," said Valencia coach Marcelino Garcia, "but our team gave everything, showing great spirit against one of the best teams in Europe."