In North Carolina, the duties of the Grand Lecturer are listed in REG. 17-5 of The Code which states:

REG. 17-5 DUTIES OF THE GRAND LECTURER.

The qualifications, selection, and duties of the Grand Lecturer shall be as follows. [11-1.3].

1. The Grand Lecturer shall be a Certified Lecturer well versed in the law and customs of Masonry.

2. He shall be nominated by the Board of Custodians and appointed by the Grand Master, but he need not be installed. His term of office shall expire with that of the Grand Master appointing him. If he shall have served three consecutive terms, he shall not be eligible to succeed himself. [11-11; 13-2.6; 29-6.1].

3. He shall supervise and assist the District Deputy Grand Lecturers in their visitation, inspection of ritualistic work, advise, instruction, and promotion of the lecture service among the subordinate lodges.

4. He shall direct the exemplification of the Authorized Work when requested to do so by the Grand Master or by the Board of Custodians, or when he deems it necessary or advisable. [24-1].

5. With the approval of the Board of Custodians he is authorized to call upon Certified Lecturers to assist him, from time to time, in promoting the lecture service. [29-10.3].

6. He shall be subject to such directions as the Board of Custodians may from time to time promulgate.

In a nutshell he sets the portions of the ritual to be instructed for the year and sees that the District Lecturers hold the Schools of Instruction for the topics.

Grand Lecturer

Shall Visit and Instruct Lodges.

Each lodge in this Grand Jurisdiction shall be instructed at least annually by the Grand Lecturer or District Lecturer unless the Grand Master shall otherwise order. The Grand Master may, in his discretion, order additional instruction in any lodge upon such terms as he may deem proper. Lodges desiring additional instruction may obtain it by arrangement with their District Lecturer.

District Lecturer.

The Grand Master shall appoint a District Lecturer for each Masonic District in the state. The Grand Lecturer shall recommend to the Grand Master names for possible appointment as District Lecturer. Each District Lecturer will be responsible to and under the supervision of the Grand Lecturer. The Grand Lecturer shall be responsible for the proficiency of the District Lecturers. A District Lecturer may be removed from office by the Grand Master without specification of charges. Any vacancy occurring by such action or by death, resignation, or any other cause shall be filled by appointment by the Grand Master for the unexpired term of office.

I almost forgot.  They judge the ritual competition.