Hi Guys.

I have the following build for MS Web Apps installed, 15.0.4641.1001.

Can i just install the latest rollup for Web Apps, or do they need to be done in order?

You'll need to install WAC 2013 SP1, then you can install a subsequent CU, if you want (e.g. August 2015).

Note that you must rebuild your WAC farm when you install a patch of any kind.

Thanks and noted.

I believe my version is post SP1. Anyway I can confirm?

Search for it, or look in Programs/Features -> Installed Updates.

Or go to http://sharepointupdates.com/Patches and search for your (partial) build number to see what patch it belongs to.