Q.why does my rose bush have no foliage, yet it bears a small amount of roses
Why does my rose bush have no foliage, yet it bears a small amount of roses.

There can be several reasons why your rosebush has little to no foliage, the top two are either black spot fungus or a major insect or slugs attack. Here are some links to articles for you, these should give you some information to help:
https://www.gardeningknowhow.com/ornamental/flowers/roses/leaves-falling-off-roses.htm
https://www.gardeningknowhow.com/ornamental/flowers/roses/rose-bush-diseases.htm