These two words are a common source of mistakes. The word you will need most of the time is “analogous”, which means “similar, comparable in some way”, as in
“Analogical”, on the other hand, means “related to or based on analogy”. For example,
“Analogical” in the first sentence refers to analogies Roman lawyers used in their reasoning. The latter sentence would only make sense if we had spoken about another kind of reasoning before and wanted to express that Roman lawyers used reasoning analogous (similar) to the one already mentioned.