The Hollywood pair announced their engagement earlier this month, and Roberts, who has three children, was delighted to hear the news because she knows exactly what to offer them as a present.
"People are starting to ask me and put pressure on me. Babysitting. Yeah, that's good," she told E! Online.
Congratulating the pair, she added, "Oh yes, it's exciting news. It's always nice when you're ready to hitch your wagon for eternity to somebody."
No wedding date has yet been announced.