To cast a Room spell, choose a half (or "door") to cast. There's no way to cast both halves of a Room card. When the Room spell resolves, the corresponding door becomes unlocked as the Room enters.
Moldering Gym // Weight Room
Because the permanent is on the battlefield both before and after it's turned face up, turning a permanent face up doesn't cause any enters-the-battlefield abilities to trigger.
If a double-faced card is manifested, it will be put onto the battlefield face down. While face down, it can't transform. If the front face of the card is a creature card, you can turn it face up by paying its mana cost. If you do, its front face will be up.
Magic: The Gathering · ™ & © Wizards of the Coast · Illus. Helge C. Balzer
Card data via Scryfall. Rarix is fan-made; not endorsed by the rights holders.
