Rāmānuja’s theory of the self seems to have been greatly influenced by the need to reply to the Advaita Vedāntin claim that the self is nothing but sheer consciousness. Thus, Rāmānuja (like Yāmuna before him) stresses the fact that consciousness needs to inhere in someone and that therefore the self is a cogniser (jñātṛ) rather than sheer cognition (jñāna).
This being said, some statements of him in different contexts may appear puzzling. His summary on the self in the Vedārthasaṅgraha, for instance, goes as follows:
ātmasvarūpaṃ tu devādidehavilakṣaṇaṃ jñānaikākāram. (VS 246)
By contrast, the nature of the ātman has the form of cognition only, and is different than the body of deities, [human beings, animals and other conscious beings].
This seems too much an opening towards the Advaita Vedānta position. But perhaps the context (explaining the dependence of the self on the Lord) was far enough from Advaita Vedānta to solve any ambiguity.