Although this miniature has the sitter's name on the reverse, it has proved difficult to find out anything about him. At top left it is inscribed either "Rev Mr Roush" or "Rev Wm Roush", or less likely "Routh".
Without being exceptional, the miniature is well painted and the pointed shape of the nose is reminiscent of the work of James Peale (1749-1831) of Philadelphia. For example, a portrait said to be of James Ladson painted by him in 1799. Peale did his best work between 1786 and 1805, and in his work after 1805 he is said to have been assisted by his daughter Anna Claypoole Peale (1791-1878).
The pose of this miniature is similar to that of miniatures by both Peale and his daughter, and if a joint work would be less likely to be signed. From the discussion about casework as below, it is believed the miniature probably dates to 1810-1815 and was probably painted in Philadelphia.The name Roush, changed from Rausch, did occur in the Philadelphia area. He is likely therefore to be related to John Roush or Jacob Roush, both of Philadelphia, who were born in the mid 18C and died after 1815.
One way to date the miniature is by studying the casework which helps to confirm it as an American portrait. I have discussed elsewhere the effect of the 1808 Embargo Act on American miniature portraits. As a consequence of the trade war, it was not possible to import cases and glasses from Britain. Hence for a period of several years from 1808-1815 miniature painters had to make cases out of whatever they could find. In this instance there is, unusually, an inner and outer glass, both with metal bezels as shown in the photographs here. It appears the miniature was made to fit the inner bezel, itself made to fit an available glass. There being no indication of any hanger. As the miniature was then too small for a standard case, the inner half-case and miniature were then placed inside a rectangular ebonised case, which appears to be more likely of French origin, trade with France being easier than with Britain. The miniature is therefore very collectible as being a good example of an Embargo Act "make-do" case. 1485