Australian Parcell, 28, has extended his stay at Hull College Craven Park until the end of 2022.
He has been one of Super League's leading rakes this term and a fans favourite ever since joining from Leeds Rhinos in 2019.
Smith said: "He’s been in great form.
"He’s been consistent and dangerous and he’s getting better. He’s still developing as well.
“As experienced as Matty is, he keeps adding to his game and that is the reason why we want him to stay.
"He’s doing a great job for us presently and we see that he is going to keep on getting better and better."
Parcell's pace and elusive running style has tormented defences but the ex-Brisbane Bronco has brought real leadership to the Robins, too.
“I think the style that we play suits Matty and the way he plays suits us, so it’s a really good fit for the two," added Smith.
"He’s a big part of us and our danger in attack.
“He’s lightning fast and strong, deceptively strong when he carries the ball and gets close to the line, wriggling out of tackles you just think are impossible for him to get out of. He really is a special talent.”