House of Thorns by Jude Knight

Retired spy, Bear Gavenor has fled the marriage mart for the familiarity of his work; restoring abandoned country manors to sell to the newly rich. Never does he anticipate that his first task will be to deal with the thief he’s caught stealing his roses.
Evicted from her home and ruined with claims she has a lover, Rosa Neatham fears she will soon be unable to care for her invalid father. When she returns to her former home to gather roses to brighten his room, her fortune worsens when she’s startled by the home’s new owner and injured in a fall.
Bear takes her in, but when the rector confronts him about living with an unmarried woman, Bear decides to halt the rumormongers’ attempts to ruin her further and marries Rosa.
He needs an heir.
She needs a protector.
Love needs to overcome the scandal, secrets and self-doubts that each brings to this marriage of convenience.