I am having tons of issues with one of my smaller Roku tvs. If I factory reset that specific tv will anything happen to the other 3 on the network?
No, a factory reset only impacts that device. It does nothing to your Roku user account, so does nothing to any other devices on that account. When you reset the TV, you will link it back to your account and all your existing channels will be reinstalled. But you'll have to add any required authentication to any channel that needs it. That doesn't transfer from your account.