Lichens are a complex living form that is the result of a symbiotic relationship between two organisms: a fungus and an alga.
Lichens do not have roots for absorbing water and nutrients like plants, but they do manufacture their own food through photosynthesis, just like plants.
They don't live as parasites on plants; instead, they use the plant's surface as a substrate.
Thus lichen does not have roots.
The absorption of water and nutrients is done by its fungal partners.