Philip Freneau's poem "The Indian Burying Ground" tells of a place where Indians, long after their death, still sit "seated with their friends." The poem, therefore, speaks to the Native American thought regarding life after death.
Later in the poem, one line states "the fancies of a ruder race." Given that a poem's interpretation depends upon how a reader interprets the poem, a single line in a poem is no different. For me, the line refers to the White Man who infringed upon the Indians' lands and lives. The stanza which the line is found in speaks to a grave stone which has been placed on the Indian burial ground. The grave stone was not a typical marker for the Indians and its presence depicts the White Man's overtaking of their lands.
While the tombstone has been partially eroded by the rain, it still represents White Man's infringement on the Indians' lands and traditions. Therefore, the ruder race is the white man.