Harry Scowen top-scored for Hastings with an unbeaten 41 while Alex Collins took 3-51 for Roffey. Rivers (102 not out) and Jibran Khan (55) saw the leaders cruise to the total.
Eastbourne skipper Jacob Smith was left stranded on 99 not out in the first innings while Ben Twine took 4-7 in Middleton’s reply.
In the only other completed match, Horsham (171-8) beat Brighton and Hove (168-7) with Sussex’s George Garton the star of the show with an unbeaten 85 in the run chase.
Ifield v East Grinstead and Cuckfield v Preston Nomads were both postponed due to the overnight rain.
New Zealander David Winn hit an unbeaten 64 as Three Bridges (116-3) returned to the top of Division 2 against title rivals Mayfield (115 all out). Bridges skipper Matt Blandford took 4-22.
St James’ Montefiore (243-8) continued their good form with an 83-run win against Bexhill (160 all out). Sam Cooper (@?57) and Henry Sims (70) starred with the bat while Sam Rattle (5-31) shone with the ball. Bexhill’s Joseph Sarro took 5-46.
Billingshurst (84-4) beat Bognor Regis after bowling them out for just 83. Andrew Miller (2-21), Andy Barr (4-28) and Ben Williams (3-9) did the damage with the ball.
Jonny Phelps hit a 58-ball 90 as Haywards Heath (191-2) beat Lindfield (186-5). Alastair Templeton (51) also contributed to the run chase.
Chichester Priory Park (169-8) beat Ansty (168 all out) by two wickets.
Division 3 West: Roffey 2nd XI v Steyning postponed; Slinfold 218-6 lost to Findon 226-5; West Chiltington & Thakeham 201-6 beat Three Bridges 2nd XI 98-9; Worthing 179 all out lost to Stirlands 238-9. Highlights George Coles 5-22 for Stirlands.
Division 3 East: Burgess Hill 188 all out lost to Hastings & St Leonards Priory 2nd XI 189-9; Crawley Eagles 153 all out lost to Portslade 225-8; East Grinstead 2nd XI 221-9 lost to Seaford 226 all out; Preston Nomads 2nd XI 254-7 beat Brighton & Hove 2nd XI 228 all out. Highlights: Lapina-Amarelle 5-17 for East Grinstead.