De Rossi was the target of Manchester United and Manchester City prior to the 2013-14 season but the 31-year-old remained at the Stadio Olimpico.
Then-United manager David Moyes was strongly pursuing De Rossi's services but the 99-time Italy international refused to leave Roma - and it has proven to be a fitting decision.
Roma are into the UEFA Champions League group stages - United are not after a calamitous season in 2013-14 - and Rossi said he had been rewarded with European football for his loyalty.
"When it was time to choose [my future], ambition was not my priority," De Rossi said.
"If you choose to stay at Roma, you don't do it for ambition. Don't get me wrong, though, Roma are ambitious, as you can see today.
"But in the past, I refused offers from some clubs that were on a higher level than Roma. It was undeniable that those clubs were a cut above Roma at that time.
"It was not my ambition or the will to win the Champions League that made me stay here but, as you know, the 30 years of passion for these colours.
"To be honest the moment we are living today is the best of my entire career at Roma. I wouldn't go as far as saying this is the best team ever but right now I feel great, surrounded by great players, a special manager.
"I couldn't possibly be happier anywhere else than I am now, here."
Rudi Garcia's men face Group E leaders Bayern Munich on Tuesday and De Rossi said he felt the Italian club were stronger than their Bundesliga counterparts.
"Roma's ambitions have changed thanks to what we achieved last year," De Rossi said of Roma's second-place finish behind champions Juventus.
"Even four years ago we had a great team that were able to make a fantastic comeback against Bayern Munich, although they had already qualified for the next round and maybe they were a bit less focussed than usual.
"Tomorrow, on the other hand, it won't be a crucial game but it will be very important for both teams and I think we are as strong as they are, if not stronger."
Roma (four points) can overhaul Bayern (six) with a win at the Stadio Olimpico.
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