Links to the Hoops have peppered the Englishman’s career so far, and he reflected on three after looking round Celtic Park and signing a contract for four and a half years on Thursday.
Roberts is one from way back, but two have played a more formative role in the 21-year-old's football career more recently.
O’Riley moved north in a £1.5m deal from MK Dons but a portion of the deal will divert back to Fulham, where he was trained, as a sell-on fee.
It is there he worked alongside Stefan Johansen after stepping up from Peter Grant’s under-23 squad.
"Peter Grant coached me during my time at Fulham in the under-23s, and he was a really nice guy who helped me develop quite a lot in my time at Fulham.
“Pat [Roberts] I went to school with. We were in the same cars to school though he is a bit older than me but he is someone that I looked up to within Fulham and he was doing really well at the time – so that’s one for the storybooks.
“And the last one is Stef, I got to know him really well. He is Norwegian and I obviously have a bit of Norwegian in me, and a bit of Danish, and we got on well in that sense but I got on well with all of them and they were good mates and it just shows you that Celtic can attract people like Stef, like Pat, like Pete and it's nice to follow the same route.”
O’Riley revealed to Celtic TV that one phonecall with boss Ange Postecoglou convinced him Celtic was his number one choice with Swansea City and Blackburn Rovers also keen on his signature.
But he admits the scale of the club ill take some getting used to.
"One of the main reasons I came here was the size of the fan base and the size of the club and even the thought of playing in front of 40,000 is a lot to me – the fact it is close to 60,000 is incredible and something I am really excited for.
“Another thing that was massive in my decision to come here – I always said I wouldn't join a club, even if they paid me a certain amount of money, if the style wasn't right. I am not that kind of guy. The style is Right Here of course and that's another reason for me to come.”
He explained: “I had a phone call with Ange and he came across really, really well. He was the one who really sold me that the club itself is massive but speaking to him really just sorted out for me, with the style he plays and all that surrounds him as a person.
"Honestly as soon as I was off the phone I was ready to come to be honest.”