There are several saints called St. Ronan, the Catholic Encyclopedia lists 12, and The Oxford Dictionary of Saints lists 4. Two referred to in Wikipedia are:

• A Cornish saint of Celtic origin, St. Ronan preached throughout his part of the Celtic Christian world, particularly in Cornwall and Brittany.

• There is a St Ronan referred to in Sir Walter Scotts book, St. Ronans Well . Scott's St Ronan was a Celtic monk who advocated the use of the Roman rather than Celtic manner for the calculation of the date of Easter. This St. Ronan is the patron saint of the Scottish town of Innerleithen. (See Synod of Whitby).

References

D.H.Farmer, The Oxford Dictionary of Saints, 1978.