Rice's theorem states that you can't decide a non-trivial property of Turing Machines in general.
You are asking, "given a specific Turing Machine, can I find some property about it." The answer is yes in a large number of cases.
Rice's Theorem says there's no algorithm which can look at any Turing Machine and find its optimum.
Your problem is to look at a specific Turing Machine and find its optimum. This is likely computable. For example, it's easy to make a Turing Machine which inputs $x$ and outputs $x^2$. Finding the maximum value of this is trivial.
The real question is: what does your search space look like? You're trying to find a local optimum? Of what function, over what inputs? If your inputs are finite and your function computable, then this is certainly decidable. If you're doing things over the Real Line, things get more complicated, but not necessarily impossible, depending on what function you're looking at.
But, if you can show that computing the optimum is equivalent to searching through an infinite search space, and you can simulate any infinite (but enumerable) search space with your problem, then you're looking at something Turing Complete, and Rice's Theorem applies.
I suggest you review Rice's theorem, to find what it's actually saying, as well as the difference between an optimization and a decision problem. Every optimization problem is most certainly not a decision problem, though you can simulate every decision problem as an optimization problem.