Rose left the Navy at the age of 19. Fortunately he had a good grasp of figures, was excellent at paperwork and was a hard worker. After a while, he was given the task of organising the printing of the records of the House of Lords which ran to 31 volumes.

In 1790 he was elected MP for Christchurch. He held that seat for the remainder of his life serving, in all, 34 years in Parliament.

He was Secretary to the Treasury for 17 years and then briefly joint Paymaster General. For 11 years he was both Vice President of the Board of Trade and Treasurer of the Navy. At the age of 65, he was offered the position of Chancellor of the Exchequer but declined it as he felt he was too old. He was a Privy Councillor for 16 years. He was also Clerk of the Parliaments from 1788 to 1818.

Rose first met Horatio Nelson in 1787 when the latter, a young Post Captain of 29, returned from the West Indies and laid complaints of laxness in enforcing the Navigation Act and of fraud against officials in Antigua. Rose, as Secretary to the Treasury, received him at six in the morning, listened to him for three hours and then invited him to breakfast with him. Rose was most impressed by the young officer's grasp of politics and the accuracy of his information. Nelson was being sued for damages of a £20,000 by some West Indian merchants and was very pleased to hear that Rose said: "Captain Nelson is a very good officer and need be under no apprehension for he will be assuredly supported by the Treasury."

Undoubtedly this relationship grew and a number of letters exist addressed to 'my dear Rose' from Nelson, a prolific writer even with his left hand.

Unfortunately Nelson destroyed most of the letters he received so we only have one side of the communication.

By 1805, Nelson had become very concerned about what would happen to his mistress, Lady Emma Hamilton, and their illegitimate daughter, Horatia, if he died. Before he sailed for the Battle of Trafalgar, he asked Rose to come to the Victory at Portsmouth to talk about it. Nelson's diary entry for 14th September, 1805 reads: embarked at the Bathing Machines with Mr Rose and Mr Canning at 2 got on board the Victory at St Helens who dined with me preparing for sea".

Nelson was shot as he walked the deck of the Victory with Captain Hardy during the Battle of Trafalgar. He was carried below. His personal chaplain, Doctor Scott, recorded that he was very agitated, saying to him: "Remember me to Lady Hamilton. Remember me to Horatia. Remember me to all my friends, Doctor, remember me to Mr Rose. Tell him I have left a will and left Lady Hamilton and Horatia to my country." Shortly before he died he said to Scott again: "Doctor, I was right George Rose has not yet got my letter. Tell him ." Nelson stopped for a while because of the pain and then continued: "Mr Rose will remember, don't forget, Doctor, mind what I say." Nelson here was referring to his last conversation with Rose the day they went aboard the Victory.

When the Victory returned to Portsmouth, Captain Hardy had himself taken 20 miles in an open boat, all the way to Lymington, and then rode the eight miles to Lyndhurst to tell Rose the news, to give him Nelson's message and to tell him about the bequest.

Rose certainly did his best for Emma Hamilton but as Pitt suddenly died two months later, he was never able to persuade his other political colleagues to fulfil Nelson's last request although they treated Nelson's brother very well. Emma appointed Rose her executor and guardian for little Horatia. Later, in her anger at her treatment, she even alienated him. She died a pauper in Calais in 1815. Horatia was looked after by Nelson's brother-in-law, Rose's co-guardian.