Solomon's son, Benjamin, lived next door to Solomon in 1850. Roxanna could possibly be a dau of Nathaniel Landreth and Patsy Bass who was separated or divorced by 1850 Nathaniel and Patsy also had a son, John. The 1850 Owen Co IN census shows John living with Patsy's parents, Edward and Polly Bass.Nathaniel had a brother, Zachariah, who could have been her uncle. Sorry I could not be more definite but I feel sure that this is the right family.
Best wishes... Eugene Landreth, Author and Compiler of "Forebears and Descendants of Landreth Pioneers".