He was sworn in on December 7, 1857 and subscribed to the oath of office on December 8, 1857.
An 1858-59 session was not held due to the protracted session of 1857-58. (Minnesota Legislative Manual, 1872, p. 66) Thus, even though the first session was adjourned on August 12, 1858; the term end date for it is listed as the day before the second legislative session's start date.
"When the State constitution was adopted, shutting Pembina out of Minnesota, it was supposed that Rolette ceased to be a Minnesota legislator. But when the legislature met in December, 1857, behold here was the "Gentleman from Pembina" with his credentials, as usual, and of course he was admitted." (Minnesota in Three Centuries, Vol. 2, p. 500)