Well, there was quite a bit or territory between the Roman frontier and Poland, but more importantly, the idea of conquering an are "for its resources" isn't really something that happened, or at least not until fairly recently. As a general rule, the cost of invasion and administration will more than outweigh the benefits of extraction, and more to the point, the state was not generally directly involved in extraction, so the prime beneficiaries would not be the state, but those elite who were positioned to capitalize on it. These elite were heavily tied to and related to the workings of the state, but they were not entirely congruent.

Or to put it differently, by and large it is easier to just trade for the material. There is really only one example of a Roman military action that is generally accepted to have possibly been for the hopes of controlling resource production, and that was expedition of Aelius Gellius in 25 BCE to Arabia Felix. The expedition was a failure and would not be repeated, a rather significant fact.