Apisonic Labs has released Speedrum Lite

[cclarry]

a free percussion sampler instrument plugin for Windows, Mac and Linux.

It allows you to drag and drop any WAV, AIFF, FLAC, MP3 and OGG files onto one of its 16 virtual pads and thus create custom percussive kits that can be saved.

https://apisoniclabs.com

[Doug Rintoul]

I had a look at this. It looks good but it does not do Round Robins. Poise (https://www.onesmallclue.com/), while Windows only, is much more versatile and is also free. 

[Wibbles]

"... Latest version: 0.6.0.8241 (alpha – expect the unexpected)"