You can do a few things to show or create rooms and room tags in your model from a linked in model.
First in your model make sure "Rooms" are turn on under Visibility Graphics > Model tab. Then turn on Room tags under the annotation tab.Then you will need to find which linked file created the rooms and room tags so that you can turn them on. The easiest way is to turn on Reveal hidden elements and hover over the room tag and tab, once you have tabbed to the room you can click on it and see from properties the information you need to know like what view the room and room tags where created in. You will notice that when you do this properties will be grayed out.
Go back into the Visibility Graphics > click on the Revit Links tab click on the Display Settings button and set the linked model to "Custom"
Since you know what level the rooms and room tags were created on, you can set the "Linked View" to the proper level.
From the Model Categories tab switch the Model Categories from <By host view> to <Custom>. You can then verify that the Rooms has a check mark. You will do the same thing on the Annotation categories tab for the room tags.
Click the Apply and OK button to get back to your model. You will now see the linked models tags. Because your model and the linked in model might have more elements in it, you will want to make your own room tags so you can place them where you want in the room. Once you have tagged all the rooms, go back into the Revit link through Visibility Graphics and turn off the Room tags.