Microsoft is terrible about changing settings with updates and not telling the user. Most likely there's a change in the Windows Firewall setting that is blocking uPNP access (DLNA is a form of universal Plug and play). UDP port 1900 is one that needs to be open, but I'm not certain what other ports WMS might use.
That said, the Windows Media Server is a very poor example of a DLNA server. It offers very little ability to transcode unsupported media, doesn't offer metadata retrieval, and in my opinion is just junk. There are far better server options available, and most are free of charge. Plex of course is a good media server, and it has the benefit of a dedicated app/channel for Roku devices (as well as almost any other smart TV or player). Another is Emby. I am partial to Serviio, and I have assisted the creator by writing the profiles used for Roku devices (but I am not an employee of Serviio). Everything I've listed here will blow Windows Media Server out of the water, and all offer free versions that work perfectly on your home network. They also offer a paid version, but the majority of users are fine using the free version.
I'm not using the actual Windows Media Server program. I just share the folder with the roku
