In 1801 he made his home at Terrebonne, Quebec, purchasing the Seigneury in 1814, although he was forced by a court action to relinquish his title to the property in 1824.

[3] In 1785, Mackenzie was employed as a clerk and as his cousin Alexander's assistant in the fur trading firm of Gregory, McLeod & Co., of Montreal.

To end the tension, Simon McTavish invited Gregory, McLeod & Co., to become part of the North West Company.

From about 1805 until 1825, he had entered into a business partnership with his brother, Henry, in the firm of Mackenzie, Oldham & Co., whose partners included the Hallowells and several other prominent fur traders.

He supported the joining of Lower and Upper Canada, and vigorously opposed the Patriote majority in the Legislative Assembly.

[1] On settling at Terrebonne he spent much of his time collecting information on the Canadian fur trade, native Indians and the natural history of Western Canada.

Much of the information that he gathered was collected and published as Les Bourgeois de la Compagnie du Nord-Ouest, by his granddaughter's husband, The Hon.

Mackenzie collected and posthumously published a copy of Simon Fraser's journal relating to his voyage from the Rocky Mountains to the Pacific coast in 1808.

[5] He is also credited as the author of the introduction to his cousin, Sir Alexander Mackenzie's, book Voyages from Montreal, which gives an overall history of the fur trade at that time.

Mackenzie intended to continue McTavish's developments and had made plans to raise the annual revenue from £1,000 to £3,000.

However, his sister-in-law, Marie-Marguerite (Chaboillez) McTavish, disagreed with the sale stating that the executors of her late husband's will had exceeded their authority in allowing it to be sold.

Roderick Mackenzie's home in Terrebonne was one of the best-known in the area, with a six-stepped porch and four white columns supporting a second floor balcony.

[6] Mackenzie's brother-in-law, Joseph Bouchette, visited Terrebonne in 1815 and remarked, "...the mansion of Roderick Mackenzie, which is worthy of remark for the elegance of its construction; indeed there are several houses in a very superior style to be found in this village, it being a favoured spot, where many gentlemen, who have realised large fortunes in the North West Company fur trade retire to enjoy the comforts and luxuries of private life".