Eighteen months ago Rowntree missed out on a place in Sir Clive Woodwards's World Cup-winning England squad, so was especially delighted to get the call last week.
"I got a phone message from Clive at 8 o'clock on Monday morning, which I eventually picked up at 8.15," the Stockton-born player told The Journal.
"He said he was pleased to tell me, after leaving me out of the World Cup squad, that I had made the Lions squad.
"He said he had quite a few calls to make that day, but he wanted to ring me first and I thought that was rather good of him and I was pleased he called me.
"I can use all the cliches. I'm over the moon, chuffed to bits, etc, etc.
"There were a lot of questions asked leading up to the Lions announcement. All I did was give the standard answer, 'There are a lot of big games coming up and that's my focus for now'.
"But it's true, you can't lose your focus worrying about selection.
"On the Monday, however, I suddenly sat down and realised I would be going on what I think will be the hardest tour ever."
However, Rowntree, who has played 20 matches for his club and seven Tests for England this term, does not intend to take his foot off the gas between now and stepping on the plane to New Zealand.
He added: "We've got some massive games between now and the Lions tour and people keep saying 'Oh, don't get injured in these matches'. I don't think like that."