The Ireland international has been a revelation since emerging through the Academy ranks at Odsal, scoring 89 tries in just 98 appearances in the lower divisions.
But Halifax-born Ryan, 23, now heads into the top-flight with the Robins on a two-year deal.
“When I arrived at the stadium, the move started to sink in and I’m really excited to be a part of something new,” he said.
“It is another step up for me, being in the Super League.
“It is something that I have never done before but I can’t wait to get stuck into pre-season.
“I was with Bradford for four years and I had a great time there. There were some highs and lows there, but this is a fresh start for me across the next two years.”
Ryan endured administration and relegation to the League 1 with Bradford before helping them get back into the second-tier and establishing himself as one of the most potent finishers in the Championship.
“I made my breakthrough in the Championship before we were relegated to League One,” added the wideman, who was 2018 League 1 Young Player of the Year.“To be part of that rebuilding process, to see where it’s been to where it can be going now, was good.
“The levels have increased each year and I’m intrigued to see how I do in this league and progress even further.
“Try-scoring is something that I pride myself on and I try to maintain the best form that I can.
“Throughout the past few seasons I’ve been Bradford’s top try-scorer and I want to keep that going here.”
He becomes KR’s fifth signing for 2020 and - with Ryan Shaw released - will be targeting a starting spot.
“I’ve previously worked under Rohan Smith, who is Tony’s nephew,” he said.
“I really enjoyed my time under him so if Tony is anything like Rohan, then I’m sure I’ll enjoy it here.
“A lot of the boys have been coached by him before and they’ve only said good things so I’m looking forward to working with him.
“Rovers did really well to battle through that relegation fight and manage to stay in Super League, which I am really happy about.
“I just want to play as much as I can in 2020 and push for a starting winger shirt - it’s a new start and new beginnings for me.”
Smith commented: “Ethan is an exciting young player that I think will have a real impact at Hull KR.
“Not only can he can score tries, as his record shows, but the other aspects that he will bring, such as his speed, makes him a very exciting prospect.
“Ethan knows that he is just starting out his Super League journey - but he’s got the right attitude and he’s hungry for it.
“He wants to further his career here and to make a successful career in Super League.
“He fits our criteria of young people that want to come here and improve themselves, and he wants to prove he’s capable of making that top-flight jump.”