Roberts was born in Loughor, near Swansea, a town of around 2,000 people at the time. He was born on June 8th 1878 in the family home called ‘Island House’. His father, Henry, was a collier. The one book he read was the Bible and he committed much of it to memory; at one time he memorised 174 verses in a week. His mother, Hannah, was a very moral person who was, like her husband, a devout Christian. She came from a large family and she herself had fourteen children, four of whom died early. Roberts was baptised at Moriah Calvinist Methodist (now called Presbyterian) Chapel in Loughor.
When Roberts was eleven his father broke his leg and on recovering he could not walk very well, so he needed Roberts to help him with his work in the mine. He was eager to work and by the time he was sixteen he had been promoted to a responsible position at the coal face. Roberts was brought up by his parents to follow the ways of God. He loved his Bible and took it down the mine with him. One day he left it in the mine and there was an explosion. The pages of his Bible were scorched and scattered, but he gathered them up and took them home. He worked in the mines until 1902. He earned good money, but was concerned that the money might draw him too far into the ‘world’. He was careful with his finances and was sure to tithe from them.