The 30-year-old thanked Hornets owner Gino Pozzo, who has pledged to put the England full-back "back on the map" at Vicarage Road.
Rose found himself surplus to requirements last season at Tottenham, and was captured on Amazon Prime Video's Spurs documentary confronting boss Jose Mourinho over his lack of first-team chances.
And he has now revealed his relief on completing a two-year deal to move to newly-promoted Watford, extending his stay in the Premier League and riding out the financial uncertainties of the coronavirus pandemic.
"Without going into too much detail I always planned to be a free agent, so that meant running my contract down," Rose told Watford's official club website.
"Pre-Covid that would have looked like a smart financial decision, but after the year that we've had, I've been sat at home waiting for the phone to ring.
"It's been a bit scary, and something that I've not experienced in my career before.
"I've never had less than two years on my contract, so I'm very, very lucky to be given an opportunity to play Premier League football again considering I've had a year of no football."
Asked what Watford owner Pozzo said to entice Rose to join the Hertfordshire club, Rose continued: "He said he wants to be the one that puts me back on the map.
"Watford have been big admirers of mine, and it's just the fact he was willing to give me an opportunity considering a year of not playing any senior competitive football.
"He wants to be the one who puts me back on the map, and I'm grateful and I fully intend to repay him for as long as I'm here.
"I've been off the map for a year which is not ideal, but I'm keen and I'm over the moon that I'm here.
"I was possibly looking to go abroad, but I've been given an opportunity to play in the best league in the world again. And I intend to take it with both hands."
Rose has previously been impressively candid about his mental health struggles in and out of sport, but his talents and abilities have never been in question.
The 29-cap full-back seemed justified in asking Mourinho what he ought to do to force his way back into selection contention, in the footage caught on Amazon.
But he has conceded he would handle certain elements differently if facing a similar situation in future.
Asked if he is always as straight-talking as in the Tottenham documentary, Rose replied: "Yeah, I think so. It's not always welcomed in all industries, but most importantly I love winning.
"I did want to play, the team wasn't doing amazingly well. And I thought I deserved to have been given a chance. But that's football. Managers come in, some like you, some don't. So it's just one of those things.
"That experience has obviously shaped me. And I'll probably deal with it a little bit better if it happens again in future."