By Susan Knox Gaby Roslin has stepped in for Zoe Ball on BBC Radio 2 after the breakfast presenter revealed her break from the show last night. Zoe, 53, will be taking time off after her mum was diagnosed with cancer and thanked longtime pal Gaby, 59, for taking the reins today. Alongside a picture of her mum Julia in hospital and surrounded by her loved ones, the star wrote: “Heartbreakingly our beautiful Mama Julia has been diagnosed with Cancer.” “As many of you know from experience, these are extremely tough times. mum is being incredibly brave. My brother Jamie & I are completely in awe o…