Rosh Hashana is actually Shabbaton Zicharon, 'Sabbath of Remembering,' in the Torah.

Leviicus 23: 23-25

YHVH spoke to Moses, saying, 'Speak to the Children of Israel, saying, 'In the seventh month, on the first of the month, there shall be a rest day for you, a remembrance with shofar blasts, a holy convocation. You shall not do any laborious work, and you shall offer a fire-offering to YHVH.'