But a stellar national carnival with Vic Country led to All-Australian selection and the flame-haired half forward from Cobden was suddenly on every recruiter's radar.
He was eventually taken by the Swans at No.6 at the draft on November 26.
"I never thought it would happen," Rohan said after meeting his new Swans teammates on Monday.
"I had a good year and got a heap of support from people back in Cobden and my family and friends."
The Geelong Falcons product said there was a simple catalyst for his rapid development from a shy country footballer into one of the nation's hottest young talents.
"Well, I grew. That was a start," he said.
"I was a shy kid but I grew some confidence from playing in the seniors [at Cobden].
"I was always up the front, asking questions and instead of being at the back of the group, I was leading the way. I stood out more than when I was just hanging back."
Following NAB AFL Under-18 Championships, Rohan said his confidence was at a high - "I thought I could do anything then" - but it was a distant memory now that he was training with the Swans.
A meal with new housemates Dan Hannebery and Daniel Currie on Sunday night helped to break the ice but he was still in awe when invited to run a warm-up lap by Rhyce Shaw on Monday morning.
"I was like, 'What am I doing here?'" Rohan said.
"I looked up to these guys when I was younger and now I'm running with them. I always had my mind on what the boys were going to think of me."
Swans coach Paul Roos said Rohan's late development meant the club was still unsure where he would be best suited at AFL level.
"At 17 or 18, you don't know whether they're going to grow; obviously they're going to put on weight but how much, you don't know," he said.
"It is a bit of a lottery at times but Gary's last eight months in the Geelong Falcons system really excelled.
"We'll probably have him as a half-forward, half-back and that's why we were really keen to get [No.14 pick] Lewis [Jetta] as a genuine wingman, half-forward coming into the midfield.
"Gary could develop into a midfielder but we're just not sure. Obviously he's got a lot of upside and a lot of work to do but he's an exciting talent."
