The two boxers have met three times before when they were amateurs, however, Roach feels this will play no part when the Chinese fighter tries to win the Thai boxer's flyweight world title in March.
Shiming, who is a double Olympic gold medallist, does not have as much professional fight experience as Ruenroeng with only seven professional fights to his name.
Roach said: "My biggest thing is I don't want him to go into the fight thinking 'I know how to beat this guy,' because three rounds and 12 rounds are just worlds apart.
"(Amnat) has had a little more experience since they both turned pro. But he has some mistakes that I think Shiming can take advantage of. But they're not the same mistakes he made in the amateurs. And the approach to how to counter those mistakes is different also. We really have to see if Shiming understands what I've tried to teach him.
Promoter Bob Arum thinks Shiming has improved massively since working with Roach. He said: "Freddie has really done a great job turning him from an amateur star to a professional. We think he fights like a real professional. We're very enthusiastic."
Arum also spoke about Shiming's attitude towards fame, saying: "I think he was used to the adulation and the attention over a long period having won two medals — that encompassed four years. So he's used to fame and fortune. He's a pretty down-to-earth kid."