The Papa New Guinea international has mutually agreed with the club to terminate his contract to travel back to PNG.
The half-back will return to his homeland today after making five appearances for Ryan Carr's side.
He scored a try on his home debut against Batley Bulldogs and kicked two conversions in the victory over Halifax.
The 30-year-old hasn't featured in Rovers' last two fixtures and was an unused substitute in the 32-14 victory over Sheffield.
A club statement read: "Everyone at Featherstone Rovers would like to warmly thank Boas for his contribution to the club and wish him and his family all the very best for the future.
"Featherstone Rovers would also like to confirm that Ase Boas’ younger brother Watson Boas will remain in the UK and is available for selection in Sunday’s match against Dewsbury Rams at the LD Nutrition Stadium."
Meanwhile, new arrival Makahesi Makatoa will be available for selection for this Sunday's clash with Dewsbury.
The Cook Island international arrived in England on Sunday after signing a deal with Rovers part way through last week.