Rousseau’s sole con­nect­ion with hymn­ol­o­gy are the related tunes Green­ville & Rousseau:

…the pro­duc­tion of that bril­liant but er­ra­tic gen­i­us and free­think­er, Jean Jacques Rous­seau. It was orig­in­al­ly a love ser­e­nade (Days of ab­sence, sad and drea­ry) from the op­e­ra of Le De­vin du Vil­lage, writ­ten about 1752. The song was com­mon­ly known years af­ter­ward as Rous­seau’s Dream. But the un­be­liev­ing phi­lo­so­pher, mu­si­cian, and mis­guid­ed mor­al­ist build­ed bet­ter than he knew, and prob­ab­ly bet­ter than he meant when he wrote his im­mor­tal chor­al. What­ev­er he heard in his dream (and one le­gend said it was a song of an­gels) he cre­at­ed a har­mo­ny dear to the church he de­spised, and soft­ened the hearts of the Christ­ian world to­wards an ev­il teach­er who was ins­pired, like Ba­laam, to ut­ter one sac­red strain.

Brown, p. 112-3

1. Greenville
2. Rousseau