YES! If you purchased a pre-book, and decide to be roommates with someone who has also purchased a pre-book, you may both apply the $250 pre-book deposit towards your shared room.
Since your prebook deposit lives in your account and your roommates deposit lives in their account, the only way you can both use your deposits is if you each use your own account to pay. By splitting payment, your pre-book is applied to your 50% of the package, and your roommate's pre-book is applied to their 50%. Each of you will now find the details of this reservation in each of your personal accounts.
Each Bender Reservation account is identified by the unique combination of name and email address. When providing your roommate's account information for split payment, you must input their name and email address exactly as they have used it when purchasing the prebook. For instance, if your friend goes by Pam, but her legal name and Bender Reservation account are under Pamela, you MUST type Pamela. If our system does not find a name/email match with your roommate, it will assume your roommate is a new guest and create a new account for them. As such, this "new" account will not have a pre-book on file.