MSTP with no root bridge consequence

Hi guys,

I am about to configure a network of arround 30 switches in MSTP. I will create 1 region with all my vlans for all my switches. I will then elect 2 of my main switches as primary and secondary root.

Within that context, my questions are the following,

1- What will happen to the MSTP tree if my primary and secondary root switch goes down?
2- In the case of an outage, do I need to power up my primary and secondary root switch first?

Thanks in advance for your insights