According to Brian Evans in his book, Romford Collier Row & Gidea Park (published by Philimore & Co Ltd. 1994. ISBN 0 85033 922 7 ) evacuating women and children did not take place in the Romford area until JUly 1944 when some 9,847 mothers and their children left for far flung and exotic places like Barnsley, Sheffield, Middlesborough and Derby as well as places in Norfolk and Suffolk, he does not mention Wales at all unfortunately. You might want to try Simon Donoghue the local studies librarian for Havering to see if he can help (I will PM you with his details rather than give them out on an open board) you with your enquiry. Have you got the name of the school right? I live near Romford and deal with some of the areas history and can not remember, nor have come across, a school called Rohan or anything similar before now.
OR.