"Yes. I find it best if the memories have the ability to integrate on their own rather than being forced." Once he had at the second confirmation he went ahead with the spell work. The memory drifted from the penseive and traveled right for Roger's head. Strictly speaking he didn't know exactly what was going to happen, but he had a good idea.
And even if he wasn't being completely honest, as far as he was concerned it was a good cause. Both he and Samara were in danger of dying and anything he could learn to stop that was worthy.