Different spanning tree protocols behavior

Hi,
This is my first time posting a question, so apologies if I missed something.
My question is...
I noticed a weird setup at my workplace and i'm unsure of how STP will interact. We have about 15 switches spread around the network, and I have noticed some run PVST and others run RSTP. I also noticed that there will two root bridges for a particular VLAN. However one root bridge will be running PVST and the other one will be running RSTP. What happens in that time of scenario?
Is it that only PVST switches will look at the root bridge running PVST and the ones running RSTP will look at the root switch running PVST.

It usually happens when people add additional switches over time and configure them using RSTP.
You then end up with a mix of the two.
As Reza has said, schedule a maintenance window and get them all over to RSTP (or Per Vlan-RSTP). There could well be a blip during this time so I would avoid doing it unless you have advised users of potential down time.
You may find things improve after you change it, you could well have some sub optimal traffic flows if you have root bridges all over the place. 

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    Disclaimer
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    Liability Disclaimer
    In no event shall Author be liable for any damages whatsoever (including, without limitation, damages for loss of use, data or profit) arising out of the use or inability to use the posting's information even if Author has been advised of the possibility of such damage.
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