rafsi are affixes because you join them together to make longerwords. They are not words in themselves; they cannot be spoken assingle words. I don't get how you see rafsi as root words, as theyare not words at all.
gismu are called root words because they are the roots of meaning inthe language (discounting fu'ivla).
Isn't an affix something to be "added" to a base word and alter its original grammatical nature (like the English "-er" in "longer" or the Czech "nej-" in "
nejhorší" or the Japanese "sa-" in "samayou")? If it is that rafsi are to be "joined" together to make longer words, mustn't they be certain "root" words themselves from which that resulting longer words' meanings would derive, possessing proper semantic essences even though they are not to be spoken as single words. If it is a convention to not use rafsi individually, still that doesn't stop them from possessing the nature of base words. You said gismu are "root words" because they are the roots of meaning; rafsi
too are the roots of meaning, aren't they? If not, how could we possibly read the meaning of a lujvo which are made from rafsi? rafsi have
meanings by themselves, and therefore they are words. Or, rather, root words, since their forms are the most basic and simplest of the lojban words which have "real contents". rafsi may have been invented after gismu, but phonemecally it's rafsi which are fundamental and carry the semantic basis of every possible meanings in Lojban, isn't it? That's why I've had the impression of rafsi to be more like "root words" than gismu are generally assumed to.