Wales Under-21 marksman Cassidy hit a hat-trick at Prenton Park on Saturday, while Zoumana Bakayogo was also on the scoresheet for unbeaten Rovers.
The margin of victory would have been more but Jean-Louis Akpa Akpro's brilliant solo effort struck a post.
Yeovil occupy second place after claiming victory over Doncaster thanks to goals from ex-Rovers striker James Hayter and substitute Gozie Ugwu at Huish Park.
Lee Hughes and Alan Judge were on target in a 2-0 win for Notts County that ensures Bury remain winless in League One.
County went ahead through Hughes after 76 seconds, the striker reeling away in celebration after the very slightest of touches to divert Judge's free-kick past Trevor Carson.
The visitors sealed victory when Judge collected a through ball from Andre Boucaud to punish Bury on the break.
Nicky Ajose helped promoted Crawley continue their promising start to the season with a third win in four league games, beating visitors Leyton Orient 1-0.
Ajose, on loan from Peterborough, struck in the 72nd minute with a well-placed low shot after being set up by substitute Michael Jones.
Sheffield United kept their unbeaten start to the season intact with a thrilling 5-3 win over Bournemouth at Bramall Lane.
Tommy Elphick put the Cherries ahead before a Ryan Flynn double in the space of seven first-half minutes gave United the lead.
John Cofie extended that, but Lee Barnard reduced the deficit only for Richard Cresswell to restore it. Marc Pugh made it 4-3, but then Nick Blackman's penalty late on made the game safe for the Blades.
Darius Charles' superb solo effort saw Stevenage draw 1-1 with Shrewsbury after Paul Parry had sent the visitors ahead.
Luke Chadwick scored his third goal of the week to set MK Dons on their way to a comfortable 2-0 victory over Carlisle.
Max Clayton's first-half strike secured Crewe a 1-0 victory and left managerless Coventry still looking for their first league win of the season.
Brentford secured a late 2-2 draw at Walsall when Clayton Donaldson nodded home on the stroke of full-time.
Jonathan Franks and Luke James earned Hartlepool their first win of the season and piled the pressure on Scunthorpe boss Alan Knill, who saw his side slump to a 2-0 defeat.
Portsmouth's misery shows no signs of ending after Oldham's Jonathan Grounds fired them to a 1-0 defeat at Fratton Park. Jordan Obita and Cliff Byrne were sent off as both sides finished with 10 men.