What killed 5 of my rose bushes?

I've been growing roses in Redwood City, CA for decades. Many of my rose bushes are several decades old, but still doing well. This past fall I lost 5 of my rose bushes which were all growing in a relatively sunny area of my backyard: Leander, Emanuel (English roses), Fashion, Hot Cocoa and Gruss an Coburg. They were all quite healthy, but suddenly started to fail. Within a month, all were dead. I inspected them for insects, but didn't see anything. I kept them well watered during our very hot weeks. Some roses growing very close to them were not affected, but of the same age. Today (12/24/22) I walked out side and saw mushrooms growing at the base of all the dead rose bushes. So my question is, "Did fungi kill my rose bushes or are the mushrooms growing as a result of the dead bushes rotting away?" We had a good rainy spell during the first week of December and the ground is still quite wet. I've attached some pictures. Don't know what kind of mushrooms these are. So I won't be eating any as much as I love mushrooms. I have disposed of all the mushrooms, but have not dug up the roses in hopes that a twig or two may survive. Doesn't look promising at the moment...

Hard to tell after the fact what killed your roses.  Usually looking at the stems and leaves offer some hints. i highly doubt yours are coming back. If they do and if the roses you planted were grafted ones as many are, all you will get are Dr. Huey roses.

Generally speaking, if I had 5 roses die suddenly, I would dig them up carefully, including all the dirt around roots and carefully bag it all to dispose of it all out if my garden.  Any clippers I used I would either toss or sterilize either in bleach or in boiling water.  I used to carry a spray bottle of 10% bleach with me as I went from plant to plant, spraying my clippers between plants.  I would avoid planting a similar plant in that area.

Usually growing mushrooms mean there is rotting organic matter they are feeding on, like rotting roots.  When you say you watered them frequently when hot, did you check your soil under each plant to make sure the soil was not waterlogged before you watered so much?  If your bed does not have good drainage, you will rot the roots if you keep them too wet and that can quickly lead to death.

There is a fungal disease caused by mushrooms in the genus Armillaria, honey mushrooms.  Roses are very susceptible to this.  https://www.gardenersworld.com/how-to/solve-problems/honey-fungus/

If you google 'honey fungus' you can see the different mushrooms in this genus.  It spreads underground killing the roots.  I cannot ID mushrooms so I am little help.  If your roses died because of this, the honey colored mushrooms usually appear in autumn by the canes like yours did. 

I wonder if you sent those photos and story to your local agriculture office or even the UCCE Santa Clara county, you might get some educated answers.
https://mgsantaclara.ucanr.edu/contact-us/ask-a-gardening-question/
https://cesantaclara.ucanr.edu/Programs/contact/

Merry Christmas, Happy Holidays Kimmy! May your garden in 2023 be your best yet!

Zilly Zilly, thanks so much! You are a fountain of good information. I will follow your advice. Once I left the hose running too long and things looked a bit flooded. Perhaps you're correct that I killed them with kindness (or a distraction). But others growing right in the same area survived. I guess it will continue to be a mystery. This garden is in San Mateo County, but your sources are good ones. I noticed that there are two different kinds of mushrooms in my photos. Strange. The rose bush with the toadstool looking ones looks like it might have a stem or two still alive (Hot Cocoa). That's a very thorny rose, but I love the smokey burst orange color. Thanks again. Happy holidays and new year!