The room is locked. The room should be locked. Lock the door.

You're not wrong to ask about what "to be" means here, since it's a little complicated. In your sentence, "to be" essentially means, "Something is expected to happen at a future time." When we use this construction in English, it's a comment on something that will happen in the future. In your sentence, "to be" means: "The room is expected to be locked in the future [but it is not locked right now]." Here is another example. If you break your iPhone, you might call a repair shop. The repair woman tells you: "Bring your credit card and the phone to be repaired." That means your broken phone, which will be repaired in the future. If you're doing a search online, you want to search for the "be + to construction."

Please translate that word in English so I can answer your question properly.