Is it the sound or the response you're having problems with?

On my Yamaha kit, I found it was best to tweak the ride sounds while using a tom pad to trigger the sound.  The tom pad provided a more consistent response.

Then I realized I was a lot better just using  a tom pad for the ride altogether.  The cymbal pads are fine for crashes, but not good enough for a ride.

I would expect more from your kit, though.

I can't offer much help on the TD-8 since I don't have any experience with it. But I've been pretty pleased with some of the stock cymbal sounds on my TD-10 with TDW-1 epansion kit. Although there's still a lot of tinny sounding cymbals in the collection. I've found about 3 kits I like for most of the songs my band plays. And I like the stock settings for the cymbals. A roll on them is about the only thing that doesn't come out well, and with a little experimentation I hope to overcome that effect some day.

If ALL the rides you can choose from in the TD-8 are sounding "tinny" to you, it may well be your phones or monitor(s) as suggested above.  If you are using phones, consider recording a sequence using your current favorite ride sound and loop it, then take the module down to your local music/hi-fi store and try out a variety of phones to verify if this is indeed the problem.  

If it is, you still could try to EQ it away, although, I think that a good set of phones may also make enough of a global difference to justify the cost.  I've compared a lot of phones and to my ears, the Sony 7506s are about the best value for money for monitoring drum modules at under $100.  Your mileage may, as always, vary.  

If you are using monitors and find they are the culprit, a little EQ, something like a BBE sonic maximizer (or reconsidering monitor choice) may be alternatives to explore.

The cymbal sounds that you get with the TDW-1 upgrade (only for TD-10) are truly much better.  As far as modules go, they are some of the best so far.  However, I much prefer some of the great sample sets out there to any sounds (drum or cymbal) that I've ever heard from any module.

If your cymbal doesn't trigger well, that's a separate issue.  Don't know what you mean by Roland PRO, but the current Roland ride triggers extremely well (although I have physically modified mine to improve it even further but that is another story).