A brutal way:
1 Select>Hierarchy;
2 Display>Show>Show selection (let's hope that no visibility channels are locked and no display layers are off);
3 In perspView panel menu Show>None, Show>Joints;
4 If joints are too small/big go for Display>Animation>JointSize...
Now it should be obvious that root joints are those with no incoming spikes from other joints. Once you have determined how many there are, you can make one überRoot. The trickiest part is to gather those minor roots under it without ruining the rig's functionality.
,,,_°(O__O)°_,,,
Maya2019.1 @ Windows10 & GeForce GTX1080Ti
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