Or search: richness, formality, grandness, magnificence
2 Syllables: SU
alias, aqueous, atheist, patriots, radius
3 Syllables: SUU
laziness
3 Syllables: USU
compatriots, cutaneous, extraneous, spontaneous
4 Syllables: UUSU
instantaneous, miscellaneous, simultaneous, subcutaneous, subterraneous
5 Syllables: UUUSU
contemporaneous, extemporaneous

Found 17 words across 5 groupings. Skipped 1 excess word of a similar stem.