The integer roots of the polynomial function can be only among the divisors of free term.
The divisors of free term are:
Check them:
1. , 1 is not a root.
2. , -1 is not a root.
3. , 2 is not a root.
4. , -2 is a root.
5. , 3 is a root.
6. , -3 is not a root.
7. , 4 is a root.
The cubic function has at most 3 roots, then
roots of the function are -2, 3 and 4.