In addition, he was a member of various committees, and was one of the founding members of the Irish Shows Association -- holding the position of national chairperson between 1990 and 1991.
One of Derek's first successes at the Dublin Horse Show came in 1975 when he produced a homebred three-year-old gelding by Master Buck to take the reserve sash in the Young Horse Championship. That runner-up placing was to be matched, and bettered, many times by his horses until his retirement from the show ring in 2000.
One of those was the homebred Greenhall Light, who won the Pembroke Cup in 1983 and then clinched the Supreme Tricolour 12 months later for his new owner.
He was particularly proud of the fact that several of these went on to win under the saddle, both in Ireland and across the water in England.
One in particular was a gelding by Varano, who won the All-Ireland two-year-old final at his local Tinahely Show in 1988, before going on to place second at the RDS.
Sold soon afterwards to John Dunlop, he was named Jack Horner, and went on to win numerous championships in England, including one at the hugely popular Horse of the Year Show.
Jack Horner's dam, Miss Muffett, was another top broodmare who also bred the British-based stallion Tinahely, as well as Darantus Flight, dam of the stallion Barnaby Flight, and Greenhall Miss Flight, dam of the three-star event horse Brave Heart and show horse Will To Win.
Though the Breeders' Championship was one to elude Derek, his son Derry twice brought home the honours. Having first won this title back in 1998 with Greenhall Cailin Deas and her Cruising filly foal, he was thrilled to bring the accolade home once again this summer with that same filly, now named Millennium Cruise, and her April colt by Mermus R.
The mare had placed third in 2010, with a filly by Harlequin Du Carel, but prior to that won in hand as a two-year-old and again at four with a foal at foot.
Of course, that Breeders' win came on a day when Derry, along with Emily, Sharon and Mary, also celebrated winning the Owen Ryan Perpetual Challenge Cup for the second year in succession, this time with their three-year-old filly Indicator.
Twelve months earlier, this had been awarded to Greenhall Stormdancer, who is now breeding at the farm.
By Limerick, out of Weavers Wonder, by Weavers Web, and bred by Lorraine Wallace, striking bay Indicator was an All-Ireland yearling champion and placed second in the equivalent the following year. On top of that, she remains unbeaten at Balmoral, having won as a yearling, two and three-year-old, and en route to Dublin won the tricolours at Enniscorthy, Gorey and Tattersalls.
She is in foal to the Rothwells' resident stallion Greenhall, who carries superb breeding as a son of Crosstown Dancer, out of Cailin Deas, and a half-brother to Millennium Cruise, Greenhall Dot and Greenhall Miss Cruise.
Apart from the RDS accolade won in 1998, Cailin Deas herself was a multiple winner as a young horse, winning the All-Ireland titles as a two and three-year-old. By Mr Lord, out of Bassom Lady, by Bassompierre, she was closely related to Robert Splaine's showjumper Big Ed.
As well as Mr Lord, Weavers Web also proved hugely successful as a sire for the Rothwells over the years, not least through Flowing River, who created history by winning All-Ireland titles as a foal, yearling, two-year-old and three-year-old.
Bought as a foal by Willie and Ann Lyons, she was also the supreme young horse at the RDS as a yearling and again as a two-year-old, and was champion filly 12 months later.
On retiring, she returned to Tinahely to start breeding, but sadly her last foal was to be the All-Ireland and Balmoral three-year-old champion Greenhall Dismissed. She continued her winning ways at the RDS this year and landed her middle/ heavyweight hunter broodmare class before coming so close to providing the family with a fourth title by claiming the sash for the reserve champion hunter broodmare behind Rosemary Connors' Woodfield Valier.
By Porsch, and a previous class winner here in 2009 and 2010, this year she was shown in-hand with her filly by Ghareeb.
Tragically, Flowing River was killed by lightning the year Greenhall Dismissed was born, but these superb bloodlines carry on through her progeny, and that of her siblings out of the great show mare Barronstown Girl, by Touchstone.
These include Flowing River's full-sister River Tak, winner at Balmoral as a foal and yearling; and full-brothers Derry M (Bewleys Hotel) and Bewleys Ballsbridge, who between them won numerous titles.
When Weavers Web died, Barronstown Girl was covered by Van Dantzig, and this resulted in yet another show winner, Tinahely Times.
The Weavers Web line also continues at the Rothwell farm through daughters of Mangan Samba, who produced several successful event horses over the years.
This mare is now one of 20 in the breeding herd that also boasts traditional bloodlines, carrying sires such as Crosstown Dancer, Rich Rebel and Kildalton Gold. His dam, Kildalton Countess, also produced Kildalton King, and a granddaughter of 'Countess', by VDL Arkansas, continues this famous line as a broodmare.
Another is a premier coloured mare by Frankfort Boy, and a daughter of Delamain, previously showjumped by Emily, who still competes at riding club level.
Of course, this successful breeding operation would also not be possible without the knowledge passed on by Derek to his son Derry, and now to daughters Mary, a schoolteacher by profession, and Sharon, also a successful breeder of cattle.
However, the talents certainly do not stop there, and Noel's sons have equally enjoyed many successes in recent years.
Ronan now runs the successful Boleybawn Sport Horses, which specialises in show-jumpers, while Philip switched to thoroughbreds in the late 1990s and has since trained more than 300 winners on the track, including that of the La Touche in Punchestown (Little Len), the Paddy Power Chase at Leopardstown (Black Apalachi), and the Sporting Index at Cheltenham (Native Jack).
The sad departure of Derek has ended one chapter of the Rothwell story, but in the years to come there will be many more as the legacy lives on.