You are not alone. I’ve read several posts about issues with IOS 13.4.1. Don’t know what the time frame is to fix the problem. Do you have an Android or windows device to use as a remote?
In order for Roon’s @support team to better assist you, please provide a brief description of your current setup using this link as a guide.
Make sure to describe your network configuration/topology, including any networking hardware currently in use, so they can have a clear understanding of how your devices are communicating.
Hard wired - Core, Sonos Beam, pair of Sonos Play 1’s, Sonos Connect wired into a Marantz amp
WiFi - Sonos One
App crashes on iPad Pro and iPhone XS Max when using any of the above, running iOS 13.4.1
Library is a combination of SSD (external) plugged into the Core and a linked Qobuz account, app is crashing on both - 11,000 tracks in total, approx 8,000 of which are on the SSD
Is there any change in behavior if you perform a full reboot of the Core and iOS device?
Does the same behavior occur if you try to reinstall the Roon app from the Apple App Store?