While I tend to use UMD gear quite a bit on my barbarian, on a rogue, getting a decent UMD score with skill and gear is quite easy. Let's look at some of the easy stuff at level 20:
23 base
3 persuasion
(8 base CHA + 6 item + 2 tome) 3 CHA
4 Greater Heroism
5 rogue action boost
1 good luck
1 rogue skill mastery
That alone would be enough to UMD Level 6 scrolls and wands without failure. Now, with a bit of challenge, you might be able to hit these UMD marks:
6 Triple Positive or Air Greensteel item
1 +2 exceptional CHA
3 Enhancement Bonus
Additional +1 from Good luck +2
1 Yugoloth Potion
Additional +2 from competence +5
When it comes to the gear mentioned, the good luck +1 bonus can come from either crafting or from Delara's tomb end-reward. You can get a persuasion item from either VoN 5-6, the circlet of persuasion, or by crafting. Obviously the greensteel items come from shroud, and for the exceptional CHA, you can try getting a ToD ring and craft it on there or a greensteel weapon. However, I wouldn't recommend crafting a greensteel weapon because the only three sources of good luck +2 is either getting the reavers trinket, a dream edge with good luck +2 or crafting. The enhancement bonus can come either from the epic spyglass from ye 'ol crystal cove or malacia's hat. If you really want to, you can try going for the seven fingered gloves from the titan raid, but good luck with that.
One thing to keep in mind is that you don't need to wear your UMD gear all the time. Heck, just keep your combat gear on, and when you need to UMD something, just put it on and scroll/wand away.