The shepherd is promising an impossibly perfect natural world to his beloved. He is desperate to have her, so he paints a utopian picture of the world she and he might share together. He supposes that he can win her affection with such an idyllic description of their potential future.
Within these various locations in nature, the shepherd promises "pleasures," and this suggests sexual overtones. He is promising grand locales, but that sexual theme is there as well, so he is also promising sexual pleasure. Note that he asks her to be his "Love" and not his wife. This supports the notion that his desires are sexual and romantic.
He doesn't just promise a bed of roses. He promises many beds. He is overdoing it again but he is desperate to have her. The "bed" is sexually suggestive and the roses symbolize love and romance.
He even promises her dresses, silver plates, and an ivory table. His fellow shepherds (swains) will sing for her every morning. All of these promises are products of his imagination. He has conjured these images and promises in an attempt to seduce his beloved. The dramatic lengths he goes to in conjuring these elaborate scenes shows how much he wants to be with her.