When you say “Roon took 3 minutes to start from the iPad”, can you clarify the error state a bit?
Does this behavior only occur when the Nucleus is first powered on for the day or does it seem to randomly occur throughout the day (after the Nucleus has been on for a while)?
What is the sequence of events here? You click on the Roon app and it hangs on the “Choose your Core” screen? Or on the spinning Roon logo screen? Does it crash immediately?
Please provide more info regarding your network. What is the model/manufacturer of your router? Is the Nucleus connected directly to the router or do you have any switches/range extenders?
If so, what are the models? How is the iPad connected to the network, is it connected to the router or to some kind of access point?