Complex sentence: She remained off the coast with a small squadron under Lillicrap to protect the troops and, with "Rosamond", to cover the eventual evacuation of King Gustavus in a Swedish frigate.
Split into simpler sentences: She remained off the coast with a small squadron under Lillicrap to protect the troops. With the assistance of "Rosamond", "Dispatch" covered the eventual evacuation of King Gustavus in a Swedish frigate.