He printed and published in Shrewsbury his Grammadeg Cymraeg , 1728 ; a second edition was published at Carmarthen in 1824 . With the collaboration of John Williams , Witley , Salop , he produced and published an English and Welch Dictionary , of which three editions appeared. He had before this begun to prepare, print , and publish his series of Welsh almanacks , which, beginning with the one for 1715 , continued to be published until 1735 (for 1736 ) — nearly all from Shrewsbury .
The other well-known almanack-maker , Thomas Jones of London and Shrewsbury ( 1648? - 1713 ) , had included, in his anthology called Carolau a Dyriau Duwiol , 1696 , three carols written by Roderick ; other examples of his work appeared in his own almanacks but many remain in manuscript (see below). He was closely associated with the local eisteddfodau of his period, from that held at Machynlleth in 1701 onwards; his almanacks provided him with an opportunity to draw attention to those gatherings and to print some of the poems occasioned by them. His almanack for 1726 contains ‘ Englynion o Fawl i'r Celfyddydgar Gadairfardd John Rhydderch. ’
He published a paper on arithmetic c. 1716 . This may have been the first discussion of arithmetic in Welsh but there is no copy extant. It is mentioned in John William Thomas ( 1805 - 1840) , Elfennau Rhifyddiaeth ( Caerfyrddin , 1832 ), 6, and John Roberts ( 1731 - 1806 ) , Rhyfyddeg neu Arithmetic ( Dublin , 1768 ), iii.
Some of the various printed books for which his press was responsible (from 1715 to c. 1728 ) are noted in Ifano Jones , Hist. of Printing in Wales and Monmouthshire , where also is found an account of how Lewis Morris thought of getting John Roderick to look after the press which he proposed to establish at Llannerch-y-medd , Anglesey ( Morris 's prospectus with its reference to Rhydderch as ‘a native of Mountgomeryshire ’ and as an old man in reduced circumstances, is dated March 1732 ). By the end of 1733 , however, Rhydderch was in Carmarthen arranging for Nicholas Thomas to print the 1734 almanack. In 1735 he was back in Cae Talhaearn , Cemaes ; he was buried at Cemaes on 27 Nov. of that year.
Some writers have confused him with John Rogers , another Shrewsbury printer .
Sir William Llewelyn Davies, M.A., LL.D., F.S.A. (1887-1952), Aberystwyth
Dr Enid Pierce Roberts, M.A., D.Litt., Bangor
Dr Llewelyn Gwyn Chambers, Bangor
Published date: 1959