ADJ in n
Adjectives with other meanings
There are a number of other adjectives which have this pattern.
Even here in Britain there are new composers whose compositions are rooted in music from other classical traditions.
Many toxic substances, such as tobacco tar, are attracted to oil or fat but are not particularly soluble in water.
In the case of alone, the preposition in is sometimes followed by an '-ing' clause. In the case of unusual the preposition in is always followed by an '-ing' clause.
alone insoluble rooted soluble steeped unusual
We are not alone in suffering these indignities.
This species is unusual in preferring moister spots.