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The origin of initial rotation rates of stars, and how a star's surfacerotational velocity changes during the evolution, either by internal angularmomentum transport or due to interactions with a binary companion, remain openquestions in stellar astrophysics. Here, we aim to derive the physicalparameters and study the distribution of (projected) rotational velocities ofB-type stars in the 35 Myr-old, massive cluster NGC 330 in the Small MagellanicCloud. NGC 330 is in an age range where the number of post-interaction binariesis predicted to be high near the cluster turnoff (TO). We develop asimultaneous photometric and spectroscopic grid-fitting method adjustingatmosphere models on multi-band Hubble Space Telescope photometry and MultiUnit Spectroscopic Explorer spectroscopy. This allows us to homogeneouslyconstrain the physical parameters of over 250 B and Be stars, brighter thanmF814W = 18.8 mag. The rotational velocities of Be stars in NGC 330 aresignificantly higher than the ones of B stars. The rotational velocities varyas a function of the star's position in the color-magnitude diagram,qualitatively following predictions of binary population synthesis. Acomparison to younger clusters shows that stars in NGC 330 rotate more rapidlyon average. The rotational velocities of the 35 Myr old population in NGC 330quantitatively agree with predictions for a stellar population that underwentsignificant binary interactions: the bulk of the B stars could be single starsor primaries in pre-interaction binaries. The rapidly spinning Be stars couldbe mass and angular momentum gainers in previous interactions, while those Bestars close to the TO may be spun-up single stars. The slowly rotating,apparently single stars above the TO could be merger products. The differentvsini-characteristics of NGC 330 compared to younger populations can beunderstood in this framework.

The young massive SMC cluster NGC 330 seen by MUSE III. Stellar parameters and rotational velocities