According to the known conditions of the topic, the number in the hundredth digit is four times that in the single digit, and the number in the tenth digit is the sum of the number in the hundredth digit and the single digit. Let's assume that one digit is two.

Then 100 digit is: 2×4=8, then 8+2= 10, 10 is no longer a single digit, so it is invalid.

Then there is only one possibility: the single digit is 1, the hundred digit is 4, the ten digit is 1+4=5, and the thousand digit is 5+2=7?

So the room number is 745 1.