I think "round" is a bad characteristic. Or to put it like this, all planets probably are round but there are a lot of things smaller than planets which also are round. Too small (and too many) to be dynamically important but too big to not be round.
Take Saturn's moon Enceladus as an example, it is spherical and yet smaller than Ceres - only half the diameter.
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Take Saturn's moon Enceladus as an example, it is spherical and yet smaller than Ceres - only half the diameter.