PlantFiles: Hamburg Parsley, Turnip-rooted Parsley
Petroselinum crispum var. tuberosum

Allies: Asparagus, carrot, chives, onions, roses and tomato. Sprinkle the leaves on tomatoes, and asparagus. Use as a tea to ward off asparagus beetles. Attracts hoverflies. Let some go to seed to attract the tiny parasitic wasps and hoverflies. Parsley increases the fragrance of roses when planted around their base. Rose problems

Parsley goes well with asparagus because it repels asparagus beetles (which happen to look very cool)
Carrots go well with them.
Chives, onions, and tomatoes also work well with them.
Parsley supposedly intensifies the scent of roses.(Worth a shot)

I can't take credit for info, It's from Golden Harvest Organics LLC

P. tuberosum is cultivated for its roots rather than its leaves. The roots resemble thin parsnips and are harvested as a winter vegetable in Holland, Germany, and Poland. It became popular in Victorian England when it was introduced there in 1727.The flavor, when cooked, is described as a "nutty, celery-parsley flavor. The roots can be stored in a cool place or sliced, dried and stored.

As with most parsley, P. tuberosum is a biennial grown as an annual. It is not frost tender. Flowers appear during the summer and seeds can be harvested in the late summer and early fall. Seeds are slow to germinate and can benefit from soaking for 12 hours prior to sowing. Sow no deeper than 1/4 inch. Germination should take place in 10-25 days.