Where could I find out about Robert’s medals?
If that is him in the photo then he is not wearing any medal ribbons at that time. If he is the man born in Norfolk and was in the Army before WW1 as you suggest then he would have enlisted in 1900 but as he is not wearing any Boer War medals, he did not serve in the war in South Africa. He married Martha in Stirling in 1913 so it is likely he served his term of 12 years and then left and got married.
If he had joined his local infantry battalion for Stirling in WW1 he would have joined the Argyll and Sutherland Highlanders but that is definately not the A&SH cap badge as it was very large.
If he did mange to make it to France or similar in WW1 then he would have had been entitled to the British War Medal and Victory medal. There will be a medal card for him in the National Archives which someone like Ancestry will have access to. That will give you his regiment and possibly date of entry to France.