The former Sugababes star, who is working on her debut solo album, congratulated Roberts on her recent solo record deal via her Twitter page.
She wrote: "Congrats 2 Nicola (GA) Ive been pushing her 2 go solo 4 a while now lol I think she'll do brill. Gonna meet & play her my stuff soon 2 whoop! (sic)"
Buchanan later revealed that she attended this year's Jingle Bell Ball with longtime friend Leona Lewis, tweeting: "At the jingle bell ball with my gorgy pie @leonalewismusic having a fab time".
The singer recently claimed that people will be "shocked" by her upcoming album.