The word roisterers is playable in Words With Friends™, no blanks required. Because it is longer than 7 letters, you would have to play off an existing word or do it in several moves.
Words With Friends™ Letter Score: 10
Highest Scoring Words With Friends™ Plays In The Letters roisterers
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Seven Letter Word Alert: (22 words)
erotise, resorts, resters, restirs, restore, retirer, retires, retries, rioters, roister, rosiest, rosters, soirees, sorrier, sorters, sorties, stereos, stirrer, stories, terrier, terroir, terrors