Impressive Zoustar gelding Ronstar is tracking towards premier three-year-old races over spring after emphasising his promise with a clinical win at Rosehill.

Connections have already rebuffed offers from Hong Kong after his eye-catching debut at the same track last month, though interest could intensify after the two-year-old's victory in the Spring Carnival On Sale Monday Handicap (1200m).

"We were offered a lot of money after he won here," trainer Gary Portelli said on Saturday.

"The owners decided to keep him so hopefully he keeps winning for them. I don't want to lose him, that's for sure."

Ronstar ($5) enjoyed a perfect run with Winona Costin before hitting the line a half-head clear of Diplomatico ($5). Irish Bet ($6) was third by the same margin.

Portelli was rapt with the late-maturing swayback remaining unbeaten.

"He's a funny shape but he's got a will to win and you can't teach that," he said.

Portelli thought Irish Bet might have had Ronstar's measure at the top of the straight and he was edgy as Diplomatico surged late.

"He's a trier, isn't he. They go up to him and he just will not let them get past," he said.

Portelli might press on to a 1400m race in a fortnight, the distance he believes will suit Ronstar perfectly.

"Otherwise he's nominated for all the big ones down the track as a three-year-old," he said.