Roeder, who collapsed after the Hammers 1-0 win against Middlesbrough on April 21st, will take-over from caretaker boss Trevor Brooking on July 1st.
"My heart is A1 and I did not suffer a stroke, as is still being reported," the West Ham boss told Sky Sports News.
"There is no link between the condition I had and any stress or pressure of the job.
"The tumour was on the right side of the brain at the front. You are in trouble if it is at the back of the brain."