I think you should put them into a holding bed for a few months before transplanting them. The "bed" could be a large planter if you don't use the ground. In a few weeks you can pinch them so they bush out nicely, then later in early Autumn move them to their permanent sites. I suggest a holding bed because in my garden rose seedlings are slug delights. I do use a lot of leafy mulch and the slugs can hide under it and come out later on to munch their choice of seedlings...rose seedlings get devastated early on by the slugs. When I've used a holding bed or planter I have more control because there's really no place for the slugs to hide under leaves or wood chips.

T