Tielman Roos was born in Cape Town on 8 May 1879. He was educated at the South African College qualified as an advocate when he was only 23 years old. He opened a law practice in Cape Town, but decided to move to Pretoria, where he became a respected barrister.
Roos' political life started when he joined the Het Volk party, which was then led by General Louis Botha. He was not particularly politically active at the time, but a group called the “Young Turks” gathered around him.
Towards the end of 1912 Botha dismissed J B M Hertzog from his cabinet and Roos protested by demonstrating at the statue of Paul Kruger, which was situated in Prince's Park in Pretoria. A group of people had gathered there in protest and Ross and General C R de Wet addressed the gathering. They adopted a resolution demanding the re-instatement of Hertzog.
When Hertzog formed the National Party (NP) in the Orange Free State in 1914, Roos formed the Transvaal National Party. He was elected as the first chairman of the party in the Transvaal and in 1915 he was sent to Parliament. Roos was immediately perceived as a potential leader. He put word into action when Hertzog suggested independence from Britain and put forward a claim to re-establish the two Boer republics that had been lost during the Second Anglo Boer War. He organised appeals to the British government and accompanied the Freedom Deputation to Paris in 1920.
Roos was an enigmatic and popular public speaker and vehemently republican. In 1919 he suggested that the name of the NP be changed to the National Republican Party to clarify the political organisation's aims, but Hertzog and Dr D F Malan rejected the idea. During this period the NP was gaining power rapidly and General J C Smuts, the leader of the South African Party (SAP), and the Prime Minister, realised that without the Unionist Party's support his party could easily lose the next general elections.
The 1920 and 1921 general elections were not conclusive and it didn't seem that the NP would stand a chance of victory in the near future. Roos began then began to strengthen the NP's relationship with the Labour Party (LP), which was distancing itself from Smuts. He wanted to strengthen the NP by forging a working relationship with the LP. He succeeded and in 1923 the NP and LP joined forces. The “pact” served the two parties well and they won the 1924 elections and formed the Pact Government.
Roos and Malan were also embroiled in a rivalry and their disagreements led to serious dissent within the ruling party and the Cabinet. Roos' followers in the Transvaal saw him as the logical successor to Hertzog, but he was a contentious and opinionated candidate who strayed from the official party line on many occasions. Nationalists outside the Transvaal felt that Malan was the deserving candidate for NP leadership because he was generally more reliable than Roos. This conflict led to Roos threat to resign in 1928 in response to Malan's statement that elements within the LP was Communist.
In 1929 Roos' health began to deteriorate. He travelled to Germany for some expert medical advice and, thus, missed the 1929 general elections. He resigned as soon as the election result were in and on his return to South Africa he was assigned a seat on the Appeal Court bench.
When Britain was forced off the gold standard in 1931 the Hertzog government decided to not follow the example. This decision resulted in great economic strain, especially for South African farmers. Smuts was determined that the Union should also leave the gold standard, and Roos strongly agreed with him. In 1932 he left the Appeal Court and launched a campaign against government's policies in this regard. He suggested that the Union form a national government, with him at the helm, to see the country through the crisis. On 28 December 1932 Hertzog announced that South Africa had also left the gold standard.
When Parliament opened in January 1933, Smuts tabled the idea of a national government. Hertzog opposed this move, but eventually decided to embark on talks with Smuts. After a great deal of discussion a coalition government was formed with Hertzog as Prime Minister and Smuts as his deputy. Roos was not asked to join the Cabinet. He launched the Central Party (CP) and put up candidates for the 1933 elections, but was unsuccessful in his bid to re-enter party politics.
In 1935 Roos advised his followers to join the United Party (UP), which had been formed by Hertzog and Smuts. His health was deteriorating rapidly and he died on 28 March 1935.