Take, for example, the word "activations". It consists of a root, "act", three
derivational suffixes "ive", "ate", and "tion", and an inflectional
suffix "s". The root and derivational suffixes together are called the stem.
By this terminology the word "nuntolcadgau" has a root "cadgau", two
derivational prefixes, and no inflectional affixes (such morphemes don't
exist in Lojban).
I agree it makes sense to consider -nun- and -tol- derivational affixes,
but wouldn't {cadgau} be a compound of two roots, rather than a root?