Your possible rational roots are all of the factors of your constant over all the factors of your leading coefficient.
Factors of 27: 1, 3, 9, 27
Factors of 9: 1, 3, 9
So, we have 1/1, 1/3, 1/9, 3/1, 3/3, 3/9, 9/1, 9/3, 9/9, 27/1, 27/3, 27/9
All possible rational roots are: 1/3, 1/9, 1, 3, 9, 27