Sorry to disagree, but it doesn't matter if there is a loop or not. If spanning tree is running, there IS a root. Now if there is no loop, then spanning tree doesn't have to block any ports, but it's still running.
If the root should fail, then after the Max Age timer (20 seconds) expire on the remaining switches, all the switches will generate BPDU's announcing themselves as the root. After a couple seconds, the switches that have higher Bridge ID's will stop sending these BPDU's when they realize that there is another switch with a lower Bridge ID. During this election process, there can be a disruption in traffic flow as the new topology is determined.
