He was maestre de campo of Callao when he was named Governor of Paraguay, a province in turmoil due to the Revolt of the Comuneros.
Ruyloba was not the Viceroy's choice for Governor, but rather the Crown in Spain; it is possible that the Continental Spaniards did not have a good sense of how deeply the problems in Paraguay ran and what kind of politician would be needed to quell them.
After three weeks of assessing the situation, Ruyloba began to dispense the justice that the Viceroy had ordered on the rebels.
[1] When Ruyloba learnt about the comunero army, he attempted to rally the Asunción militia to ride and meet it, but found his own army deserting him en masse, unwilling to fight the comuneros for a governor who supported the Jesuits and had just arrested many of the leaders of the militia.
Ruyloba met with the comunero leaders in a meeting orchestrated by neutral party Bishop Arregui, known to be sympathetic to both sides.