Answer:
The empty set
Step-by-step explanation:
Roster method is simply listing explicitly all the elements in the set, one by one (writing them between two curly brackets, and separating them through commas).
We want then to list explicitly all the elements in the following set:
The set of natural numbers x that satisfy x+2=1.
So, first we have to figure out which numbers are in that set. The set is made ONLY of those natural numbers x, that when you add 2 to them, you get 1. Clearly no natural number has that property (since the only number that would give us 1 when adding 2 to it, is the number -1, which is NOT a natural number). So there aren't any numbers at all in that set. So if we were to list them, we'd just list nothing inside the set:
(which is just the empty set)