Rishabhadeva was an avatara of Vishnu as is described in Srimad Bhagavatam (5th Canto, 3rd Chapter):
SB 5.3.17 — The Supreme Personality of Godhead replied: O great sages, I am certainly very pleased with your prayers. You are all truthful. You have prayed for the benediction of a son like Me for King Nābhi, but this is very difficult to obtain. Since I am the Supreme Person without a second and since no one is equal to Me, another personality like Me is not possible to find. In any case, because you are all qualified brāhmaṇas, your vibrations should not prove untrue. I consider the brāhmaṇas who are well qualified with brahminical qualities to be as good as My own mouth.
SB 5.3.18 — Since I cannot find anyone equal to Me, I shall personally expand Myself into a plenary portion and thus advent Myself in the womb of Merudevī, the wife of Mahārāja Nābhi, the son of Āgnīdhra.
Then Sukadeva Gosvami says:
SB 5.3.20 — O Viṣṇudatta, Parīkṣit Mahārāja, the Supreme Personality of Godhead was pleased by the great sages at that sacrifice. Consequently the Lord decided to personally exhibit the method of executing religious principles [as observed by brahmacārīs, sannyāsīs, vānaprasthas and gṛhasthas engaged in rituals] and also satisfy Mahārāja Nābhi’s desire. Consequently He appeared as the son of Merudevī in His original spiritual form, which is above the modes of material nature.
Thus, Lord Rsbhadadeva was born as an avatara of Lord Vishnu to King Nabhi and Queen Merudevi.
As to his disappearance, according to the 6th Chapter, he left his body in Konka (Goa) in the presence of King Arhat:
SB 5.6.8 — While He was wandering about, a wild forest fire began. This fire was caused by the friction of bamboos, which were being blown by the wind. In that fire, the entire forest near Kuṭakācala and the body of Lord Ṛṣabhadeva were burnt to ashes.