After seeing a star forward lured away to Liverpool in the summer of 2017, those in the Italian capital scoured the market for a suitable replacement.
They invested just €13.4 million (£12m/$15m) in taking Under away from Istanbul Basaksehir.
Roma have seen a healthy return on that show of faith, with a highly-rated 21-year-old winger having delivered a steady stream of goals and assists in a role once occupied by Salah.
“It was very important for me that I was coming in to replace Salah as he did really well here,” Under told Goal when quizzed on the expectation which greeted his arrival.
“There was a lot of pressure but fortunately once I started scoring and became more involved – thanks to the help of all my team-mates – I really felt I was a part of the team.”
Under added on the progress he has made over the last 18 months: “The first six months were quite difficult because of the language and because I had to adjust. Once I started scoring and I began playing better, I felt I like part of the team.
“In my first season I had some difficulties at the start but then I was able to show what I can do. This year I've got this injury problem. Having to sit on the sidelines for three weeks has got me down a bit but I hope to be back in action soon.
Under has not featured for Roma since January 19, but has three goals and five assists to his name in Serie A and the same tally of strikes in the Champions League.
He feels as though he has adjusted quickly to the demands of life in Italy, saying of the differences between the top tier in his native Turkey: “I think both are difficult and tough, like football generally.
“The main difference is that people give youth more of a chance in Italy. When I was in Turkey, we only had three or four Turkish players around the age of 20. It was thanks to the coach that I was able to emerge. We need to give young players more of a chance in Turkey.”
While Under was making a name for himself in Istanbul, he was seeking to mould his game on that of a World Cup winner.
Asked to name his idol, Under said: “David Silva. I've always liked him.”
And among those he plays alongside at Roma, Under said of the pick of the bunch: “My favourite is Edin Dzeko because we have a really good understanding.”Roma will be hoping to see that understanding deliver more rich rewards, with Under continuing to fill the void created by Salah’s departure as Dzeko remains a prolific option in a central striking role.