Roberts established himself as one of the game's leading lights during the summer as a series of impressive performances saw him named HSBC Player of the Tour during the Lions' 10-match adventure in South Africa.
And Mapusua, who himself was arguably the most consistent midfield player in the Guinness Premiership last season, is expecting a huge battle when he goes head-to-head with the 22-year-old medical student in the Welsh capital.
"I haven't played against Jamie Roberts before, but he's a quality footballer," said Mapusua.
"He's a big man, but he has got silky hands and is deceptively quick. He and Ma'a Nonu had a real good battle last weekend.
"Roberts is the guy to get Wales going forward, which is what he's good at, and alongside him Tom Shanklin is another quality player with great feet and great hands.
"We will have our work cut out, but in saying that, we will be going out to try to do what we do best. And dare I say it, to try and entertain."
Roberts wasn't the only Welsh Lion to receive a bucket load of praise from Mapusua ahead of Samoa's first autumn international either.
Fellow Cardiff Blues favourite Gethin Jenkins, a Lions Test starter in both 2005 and 2009, has also already made a positive impression on Mapusua.
"The player I'm really looking forward to coming up against is Gethin Jenkins," added Mapusua.
"He pops up everywhere. He was great against New Zealand, making tackles that most backs would be proud of."