Romas/Romani are completely different than Pikeys/Travelers ...but there are good and bad in each group, making the two groups somewhat close in dealings with people. They good ones do drive around jobs, kind of like the Amish, they'll do anything, and do it well. The bad ones do the same thing, but you don't know until its too late that they did a crap job and then cleaned out your tool shed or garage at the same time or the next night after casing it
I don't know about in the US but in the UK/Eire anytime a dog goes missing (usually working dog types, but sometimes other "regular" breeds as well), the owner/advert poster always says "Travelers were seen in the area prior to theft", But then we don't have the dog thief problems that the UK does. One of the dogs my husband brought over with him was a barking snapping witch if she didn't know you and he wasn't around, and he encouraged it because of how bad the dog thieving was in his area.
an old friend is from a Roma family that is high up in the Roma heirarchy in the UK, and if you ever need anything done or a dog found, his dad is the man to go see. Most Romas and Travelers also tend to have an incredible amount of money on hand at all times ... the bets I've heard placed on horses and dogs would boggle the mind. I am talking an average bet can be 10k pounds on a 2 dog 3 hare run, 30k pounds on a horse race, and those are just done out on a field or road in the middle of nowhere. Cash on the barrel, right there and then, no sweat, I've been at a few. Not that the dogs are better than others out there, just they can put the money where their glib mouths are
watch the movie Snatch and you will see a pretty good rendition of the typical hard dealing, bareknuckle fighting, drinking Irish Travelers ... Brad Pitt is the main man, looking fit and pretty nice

You probably have to watch it on DVD with Subtitles unless you can understand pikey, which not many can