In the Scottish Parliament, Ruskell is the Greens' spokesperson on Climate, Energy, Environment, Food and Farming.

He sat on the Scottish Parliament Environment and Rural Development Committee and served as its Deputy Convenor.

His party colleague Alasdair Tollemache replaced him as Councillor for Dunblane and Bridge of Allan at the 2017 poll.

In March 2015, the Scottish Greens announced that Ruskell had been selected as the lead candidate for their Mid Scotland and Fife regional list, following a ballot of their members.

On 23 May he was announced as the Scottish Greens spokesperson on Climate, Energy, Environment, Food and Farming.