I would not allow them out in the free-roam space at the same time until much later in the bonding process. It is highly recommended that you do not try letting them loose in a territory-ripe free-roam space until they can get along well long-term in a neutral space (probably a bathroom). They will need to take turns in the common space. Essentially, your rabbit has played in that area for a long time, thus it is “hers”. She knows that, and upon entering your home, the other rabbit will know that. There will likely be a lot of chasing and territorial aggression if he is introduced into her territory prematurely. It is actually advised to try and “neutralize” your home as best you can prior to bringing another rabbit home, to try and ease things during bonding (though their sense of smell is so good, so I’ve wondered about the true effectiveness of trying).
In short, separate free-roam time is best.
In terms of housing the two buns in the same room as the original bun, it can be inevitable as a result of having a single free-roam bun who essentially owns all the territory. You want to be mindful and understanding if either rabbit is on edge and attempts to attack each other through any cage bars, so it’s important to implement appropriate gaps and distance barriers so that doesn’t happen.
I’ll also add that, because there can be a lot of stress for a rabbit to move into a new home, in addition to the added stress/interaction of knowing another rabbit is there, it is worth not starting bonding immediately and letting the rabbit settle in and get comfortable with the environment, I think.
The answers provided in this discussion are for general guideline purposes only. The information is not intended to diagnose or treat your pet. Seek the advice of your veterinarian or a qualified behaviorist.