What did Walt Whitman in Song of myself and Rosseau in Confessions have in common with the Romantic time period?

At the simplest level, they both had a sense of the basic
goodness of man uncomplicated by the artifical structures of
society.

Rousseau noted that the richer and more
sophisticated we became, the more we depended on luxuries and "needs" that gave birth to
structures that separated us rather than brought us together.  We were better off in the
simpler state where we ate when we were hungry and only what we needed, picking fruit or
hunting only what we could eat, not what we could acquire.  This state of nature was
morally superior to the state of civilization that Rousseau saw around
him.

Whitman had a similar vision of the unity of all man,
each of us begin a "leaf of grass," some taller, some greener, but all an extension of
the same spirit; you can see the germ of this idea in Emerson's Oversoul and many of his
other writings.  Whitman's endless catalogues of the Democratic ideal places slaves,
Indians, gays, straights --- everyone in the same grammatical structure because he saw
them as essentially the same separated, again, only by artifical social structures and
beliefs.

This common belief in the basic goodness of man
when separated from society, when joined with nature and each other, is a central
concept of Rousseau, Whitman and the Romantics.