No, please, you are indeed asking a very good question. The way I answer it is by being careful to remember that both the letter of the law and the spirit of the law come from a perfect and all-knowing God. Therefore, if they appear to conflict with each other, it must be that I do not understand them correctly. Yes, one does need to ask if rollerskates count as labor, because it is possible that my understanding of “labor” is not exactly the same as what God means by it. Therefore, one has to research the sources – which is far more than just a translation of the Ten Commandments – to understand whether rollerskates are labor or not.
Kind of like the laws of the country, if you will: you need to obey both the letter and the spirit of the law. Thus, we allow criminals to get away with their crimes because the letter of the law (they were not informed of their rights, for instance) wasn’t upheld. So, the spirit of the law and the letter of the law can come into conflict in any law code, and one wants to obey both.