HelpMeFind doesn't list any roses by those names. There are lots of roses with the name 'William' if that would help.
We put in a small mini garden some years ago. My mother's name is Rose, but we didn't want to leave out my husband's mother by calling it Grandma Rose's garden, so we simply called it the Grandma Rose garden...that made them both feel special and solved the problem of leaving one of them out.
Meg

Here is a link that might be useful: HelpMeFind

I'm sorry I also don't have any answers for you. I myself was going to do this for my children named Destiny, Daniel and Angelina. I found some roses with these names but I don't know where to purchase them from. It sounds like those kids have a wonderful grandmother. I found the names I was looking for in helpmefind. Megroses said that she didn't find your names in there though. Sorry.

I did find some roses with the name Taylor. Although I don't know what kind of roses they are.

Angela Rose Taylor
Baron Taylor
Elizabeth Taylor
Helen Taylor
Lady Taylor
Madame John Taylor
Madge Taylor
Mrs. Hubert Taylor
Pamela Jane Taylor
Wilf Taylor
They may not be miniature roses though, you may want to check. Hope this helps some.