Halliday & Matthiessen (2014: 327):
There is a related pattern in the clause which could be regarded as a circumstance of Rôle, except that it does not involve a prepositional phrase. This is the structure whereby an Attribute is added to a material process, either (i) as depictive, corresponding to the guise, or (ii) as resultative, corresponding to the product; e.g. (i) he came back rich, (ii) bend that rod straight. Typically such an Attribute appears as an adjective; the pattern can occur with a general noun (he came back a rich man/a millionaire), but the related nominal attribute is usually construed circumstantially, with as: he came back as a millionaire, it’s frozen into a solid mass (cf. it’s frozen solid).