The former Invercargill MP was the highest polling candidate.
In a surprise result, two-term chairwoman Ali Timms was voted off the council after 15 years’ service.
Ms Timms declined to be interviewed, but in a statement said she was disappointed.
"I congratulate those who have been successful and wish them well as they address the complex and difficult tasks that face them over the next three years."
Ms Timms stood in the Eastern-Dome constituency.
The council’s response to water quality issues is its proposed Southland Water and Land Plan.
Mr Roy said the region needed to diversify its land use and improve its management of water.
However, he did not think the situation warranted a cap on dairy conversions.
"There’s lots of things that can be done to improve the way that we do things.
"But from a farming perspective — and that’s where I come from — I think we are not in good shape when the most viable form of pastoral production is dairying.
"We need other competing land use areas ... we need to find some other things to do.
"Certainly there’s some areas, and the catchment to the Waituna Lagoon would be one, where if anybody else wants to do a conversion in there, there will be more stringent regulations," Mr Roy said when spoken to yesterday.
Full results: Eastern-Dome constituency — Jeremy McPhail, David Stevens; Invercargill-Rakiura constituency — Mr Roy, Lyndal Ludlow, Robert Guyton, Maurice Rodway, Neville Cook, Rowly Currie; Fiordland constituency — Ross Cockburn (unopposed); Hokonui constituency — Grant Hubber (unopposed); Southern constituency — Lloyd McCallum (unopposed); Western constituency — Nicol George Horrell (unopposed).
