Or search: rex
3 Syllables: SUU
dominance, dominant, Donovan, fraudulent, hostages, Jonathan, offices, Ottoman, prominence, prominent, promises, Protestant, Providence, Solomon, tolerance, tolerant
4 Syllables: USUU
concomitants, diocesan, emolument, improvidence, intolerance, intolerant, predominance, predominant, reconnaissance
4 Syllables: UUSU
concomitant
5 Syllables: UUSUU
cosmopolitan, metropolitan, Neapolitan

Found 29 words across 4 groupings. Skipped 2 excess words of a similar stem.