[2] She was introduced to politics in 1984 at the age of 20 when she met her husband Duncan Roy, who at that time was the New Zealand Party candidate for Awarua.

[1][3][4] Before entering politics, Roy worked as a physiotherapist, medical research co-ordinator, manager of a private kindergarten and as publicity officer for the New Zealand Portrait Gallery.

[5][6] Roy first contested Parliament as a list-only candidate at the 1999 general election, where she was ranked 10th on the ACT New Zealand list.

In her maiden speech, Roy talked of her "fervent" belief in the liberal ideals of "freedom of market, of mind, and of body".

[2] In the 2008 election, she contested the electorate of Wellington Central, a seat formerly held by former ACT leader and co-founder Richard Prebble from 1996 to 1999.

[14] In the latter two roles, Roy commissioned reviews of the New Zealand Defence Force (including a study on voluntary national service)[15][16] and of special education.

[31] Following the 2011 election, Roy was appointed non-executive board chair of the pharmaceutical lobby group, Medicines NZ.

[34] For a period after leaving Parliament, Roy also resumed her role as a reserve forces field engineer[citation needed].

Roy has appeared as a political commentator advocating for lowering the 5% threshold for parties to be represented in Parliament and for public opinion polls to be banned during the election voting period.