Robbie makes his debut on the soap this week as his mother Megan Macey (Gaynor Faye) decides to make contact with him for the first time since putting him up for adoption when he was a baby.
When Robbie later arrives at Home Farm to see his mum, an argument follows between the pair - but Megan's half-brother Declan (Jason Merrells) is determined to get them on good terms.
Shelton told itv.com: "[Robbie] comes down to Home Farm to check it out and see who she is, and it doesn't really go to plan from her point of view. He's not going to give her an easy ride, he's not going to say, 'Be my saviour'. He's going to manipulate the situation so he comes out on top. That's the sort of person he is."
He continued: "It's really interesting to play a character like Robbie. He's not like me at all. I've not been in his position - he's got nobody and he's on his own. He's quite nasty and devious, but there's reasons for it. He's not doing it because he's a nasty, nasty person - he's doing it because he's trying to protect himself.
"Ultimately people aren't just nasty for no reason, there's a reason to it. And I want to find out why he's like that - I'm excited to do it."
Shelton also hinted that Declan's partner Katie Sugden (Sammy Winward) will not be impressed by Robbie's arrival.
The actor said: "He does whatever he can to put himself in a more powerful position, just to protect himself. Robbie's trying to think how he wants Declan to feel, how he wants Katie to feel - I think she sees him for what he really is."
Emmerdale airs Robbie's first scenes tomorrow (May 16) at 7pm.
Watch a preview of Thursday's (May 17) Emmerdale double bill in the video below: