Since I have allergies, we don't let the girls <my two Rotties> sleep in the bed.
But many other people we know - both other Rottie people and people generally - sleep with their dog or cat companions. It's really not an issue behaviorally.
The issue is whether or not the dog, let's say, since this is more common - the dog feels she has owns the bed. This is likely a behavior that occurs in other instances in a situation like that. But letting the dog sleep in or get on the bed, does not, in itself lead to a problem.
When my Rotties come to me, they have been introduced to the crate already and are used to many household activities. They sleep in the crate right away at home. I also used an x-pen <exercise pen - think "playpen" for dogs - round or square, wire, connects to itself> with my current youngest and often had her crate IN the x-pen, and the pen itself was in the kitchen. We also had another x-pen in th family room, with a tarp covering the carpet. We used the x-pens with her til she was maybe 3 months old.
My Lab through rescue - he didn't know about crates, or houses in general, or really much of anything when he came to us at about a year and 1/2.
I used a crate with him right away and housetrain him and do a number of other things. He didn't sleep outside of a crate til he was about6 or 7 years actually because he was extremely, typically "Lab" in terms of chewy and mouthiness and so crating at night was the safe option. After that age, then he slept on the couch.
My current older Rottie can sleep on the couch or in her crate but she often chooses to sleep in her crate. We have both dog's crates always open to them in the dog room.