I'm going to assume that you don't need a review of the book so instead I'm going delve straight into what I find so fun about reading it. It's influence on 40k.
First. Lets talk about something that we almost take for granted these days. A galaxy spanning human empire. Yep, generally no sooner do we humans get faster than light travel than we have organised ourselves into a big old Imperium and stuck some figure head onto the imperial throne. Star Wars, Dune = Human Empire. However, Asimov's novels predate both of these making his human empire a contender for influencing all it's followers. Interestingly, in both the previous examples, the actions of the novels protagonists have hasten the empires downfall. In the Foundation series the Empire's decline is a statistical inevitability which leads us to our second point of interest.
Second. The premise of the Foundation series is that Hari Seldon has developed a form of maths that allows him to predict the future with some accuracy. He realises that the fall of the Empire is unavoidable and that it's fall would lead to a dark, barbarous age lasting 30,000 years. Hari see's an alternative though and sets in motion a plan that will cut the interregnum down a 1000 years.
Let's stop there and rewind a little. 30,000 years. Where have we seen that before? Let's flick quickly through our ageing copy of Rogue Trader....flick, flick. Empire of humanity....blah, blah....Rose to lead the human race 10,000 years ago......erm, so Hari Seldon's plan didn't work then? 30,000 + 10,000 = 40,000. Yay!! the magic number!
It would appear that Mr Priestly has read the Foundation series (as if we didn't know!). The idea that a galaxy spanning human empire declined into a dark age of barbarism that lasts 30,000 years before re-emerging back into the light is key to the 40K mythos and it would appear that it's been lifted straight out of the Foundation series, maths and all.
(Ironically this trope returns in the Horus Heresy series, specifically in the novel, Legion. The cabal, a shadowy group of aliens, forsee humanities collapse in the face of chaos and suggest to Alpharion that the Imperiums defeat is inevitable. However there are two options and long, slow and painful death or a quick defeat allowing chaos to burn itself out followed by a galactic rennaisance)
Third. As part of it's attempt to gain control over the barbarian kingdoms that surround it, The Foundation uses it's knowledge of Nucleics (it was the 50's!) to give it leverage. One of the first signifiers of the decline of the empire was that the peripheral worlds forgot how to use Nuclear power and how to look after and repair it's machines. In order to retain control of the technology that they were giving to the barbarians, the Foundation developed a religion focussed around the machines and train Priests to man the shrines of power on all the worlds where the eventually gain influence. The priests don't understand how the machines work but only how to operate and repair them and the barbarous peoples understand it even less.
Fourth. Part of the method of expansion into the peripheral kingdoms is the use of trading missions. The Traders show the Nucleic wonders that the foundation can supply and develop trade and supply agreements with the rulers of the petty kingdoms and planets. In this capacity, the Traders act as first contact for the Foundation and act with a huge amount of freedom and bring there own armed forces and ships to do so. The traders are so successful that they gather vast amounts of personal wealth and power through their work.
Rogue you say?
There is more, the threat the developing psychic humans pose to the rest of humanity for instance but I think that we've done enough for tonight. Where we can look at 2000ad and see the influence that it has had on Rogue Trader we can clearly see that added to the mix (along with a lot more by the way!) is Isaac Asimov's Foundation, without which the Empire, 40K timeline, Adepts Mechanicus and Rogue Traders would all be very different if they existed at all. If, like me, you haven't gotten round to reading this series yet. Jump to it!