Pruning Now ( August)

Hi all, very new to gardening so bear with me.

I've read the info at the top of the forum and it suggest pruning in March.

However.

I've recently taken over looking after a garden ( for an elderly friend), and some of the roses have not been pruned for years, some are 6 foot in height ( from stem to roses), can i or should i prune these now in the hope of them returning to full blossom next year.

Thanks in advance.