Why did my small roses grow multiple buds inside the middle of the already open rose?
What you witnessed happens some times when roses have been fed with high nitrogen fertilizers. Other times it is just a hiccup of nature. Those are called vegetative centers. I have seen roses do this and actually have a new cane grow up out of the center of a bloom like it was trying to grow another rosebush. Here is a link to an article about rose deformities for you: https://www.gardeningknowhow.com/ornamental/flowers/roses/rose-deformity-info.htm