Here are some definitions:
Quote Quoting Code of Virginia, Sec. 55-248.4. Definitions
..."Dwelling unit" means a structure or part of a structure that is used as a home or residence by one or more persons who maintain a household, including, but not limited to, a manufactured home....

"Roomer" means a person
occupying a dwelling unit that lacks a major bathroom or kitchen facility, in a structure where one or more major facilities are used in common by occupants of the dwelling unit and other dwelling units. Major facility in the case of a bathroom means toilet, and either a bath or shower, and in the case of a kitchen means refrigerator, stove, or sink....

"Single-family residence" means a structure, other than a multi-family residential structure, maintained and used as a single dwelling unit or any dwelling unit which has direct access to a street or thoroughfare and shares neither heating facilities, hot water equipment nor any other essential facility or service with any other dwelling unit....

"Tenant" means a person entitled only under the terms of a rental agreement to occupy a dwelling unit to the exclusion of others and shall include roomer. Tenant shall not include (i) an authorized occupant, (ii) a guest or invitee, or (iii) any person who guarantees or cosigns the payment of the financial obligations of a rental agreement but has no right to occupy a dwelling unit....
Here's the key exception from the Landlord-Tenant Act:
Quote Quoting § 55-248.5. Exemptions; exception to exemption; application of chapter to certain occupants.
A. Except as specifically made applicable by § 55-248.21:1 [early termination by military personnel], the following conditions are not governed by this chapter:...

10. Occupancy in single-family residences where the owners are natural persons or their estates who own in their own name no more than two single-family residences subject to a rental agreement....
I have not found clear authority for this type of situation, and I find the definitions reasonably clear (even if the exemption statute is not clear without reference to the statutory definitions), so I would take the conservative position and argue that under the definitions, even if we assume that you don't exceed the threshold number of properties, your renting of a room does fall under the landlord-tenant act because a rented room with shared facilities appears inconsistent with the definition of "single-family residence".