THEORY: Polysynthetic languages - used in a sentence?

/Contemporary Linguistics/ (O'Grady) gives me this example of a
polysynthetic language sentence-word (from Inuktitut):

Qasu-iir-sar-vig-ssar-si-ngit-luinar-nar-puq.

[tired not cause-to-be place-for suitable find not completely someone 3.SG]
"Someone did not find a completely suitable resting place."

... what is the root morpheme of this mess? And what, if any, is its
part of speech (/ "grammatical category")? Can this be used further in
a sentence (i.e., "qasu-etc foo")?

I can understand this as a fully inflected *sentence*, but as a
discrete word that would then be used with other words, I'm a bit
confused. :-P

 - Sai