How can we minimize roll over of a vehicle?

Assuming that the rollover is untripped (not caused by hitting a curb, divider or another vehicle), keeping the centre of gravity of the load as low as possible and as central as possible to the wheel base is necessary. 

Vehicles loaded with liquids in partially filled tanks have special problems because the liquid load sloshes changing the COG dynamically.

See here:

https://deepblue.lib.umich.edu/bitstream/handle/2027.42/1290/93802.0001.001.pdf;sequence=2