Froslass is gonna be fine in UU. Last gen, it was just really annoying because spin blockers (I don't consider Chandelure a spin blocker, it has terrible switch in opportunities against every spinner) could just stay in on spinners all day long, so the "guaranteed 2 layers" that suicide Lass can set down would basically never ever leave the field. Suicide Lass is gonna be so much worse with Defog, and I think Bulky Lasses will actually need to be played intelligently
I've been using Rose in OU and I believe spikes is still really good. It's harder to use now because it's so much easier to blow away, but it's still not that hard to gain an advantage with them. I think that if you go with a spiker this gen, you should stay 1 hazard "ahead" of your opponent, try to identify their defogger and predict when they wanna come in. Force them to make a decision: either I defog and something nasty happens to my defogger, or i switch out of this horrible matchup but spikes remain on the field. For example, if I've already put something to sleep, Skarm has a free switch in to Rose. If Rose is on the field trying to say.... hit Togekiss with a SE hit, Skarm is gonna feel very comfy switching in. I know he wants spikes off the field, I suspect Skarm is his defogger so I'll switch into Heatran. He now has to decide between blowing away spikes while taking a Fire Blast, or switching in a resist, but continue to take spikes damage.
I see some people overblowing how dead spikes are. Yeah, spikes takes more intelligence to play now, but it's hardly dead. If you stay 1 hazard ahead, it means both players have "used up" the same number of turns on hazard related moves. But, having a spike advantage puts heavy pressure on your opponent to blow them away and you can use that one defog turn to do something really brutal
You greatly underestimate froslass if you think she is fine in UU. Destiny bond is still leaving the match at 5-5 plus a turn wasted to eventually defog the field. The only defogger that doesn't cop it from a fast STAB ice-beam is empoleon, who is becoming a progressively worse pokemon in UU (Especially now with the steel nerf killing a few important resistances). Even then, empoleon, let alone any other defogger really hates a fast taunt. The bulky spin blocker is still a rage inducing pest, who fares arguably even better against defog users as well. The suicide lead will require a fair bit more prediction in using its moves, but its still going to be deadly as hell, and really shouldn't return from BL.
As for roserade...oh dear me UU is going from bad to worse in the hazards department now. With sleep powder and spikes legal on the same set, you just can't force it out with crobat or something similar to get a free defog without being screwed over by sleep. Admittedly with the sleep mechanics no longer being as harsh in gen VI, crobat works reasonably well, but that's still dangerous if there's something to swap into your sleeping crobat. Roserade could also do an annoying suicide lead set, though at least Xatu and crobat can screw that over. Spinning against roserade is still annoyingly difficult as well as even with megablastoise, the type disadvantage or lack of coverage moves to use against it (in hitmontop's case) really hurts every spinner. I strongly suspect Roserade will be deliberately EV'd this gen to specifically deal with megablastoise, and I'd back it to win against it too.
One thing that might help against spikes however is wish-passing. I actually think UU can do wish-passing really well this generation, especially if we can get vaporeon from OU (which is probably reasonable to predict given the perma-rain nerf). You can actually put together a solid triple wish pass core with vaporeon, umbreon and one of sylveon/florges/clefable. That gives you
-A slew of immunties and resistances: Immune to psychic, water, dragon. Resist fire, ghost, dark, steel, bug, fighting, ice
-Some decent disruption tactics: Foul play and synchronize + heal bell shenanigans from umbreon, scald from vaporeon, unaware from clefable to stop boosting sweepers. All teammates except for umbreon can generally fit toxic in on a set too.
-Extremely hard to break on the special side: With unaware clefable, the only serious threat I can think of is LO Shaymin, and only if it consistenly gets the SpD drop from seed flare. Possibly nidoking too, but nidoking is outclassed by nidoqueen, who doesn't have room to run a posion attack to break the fairy of the core.
-Slow pivots (all the eeveeloutions can baton pass, which could help to conserve momentum should you need it)
-SR neutrality
-Not overly affected by sticky web.
-Protect shenanigans: Useful for megamedicham and mienshao
The wish core would appreciate something to swap into ground types though, as well as a solid revenge killer to deal with the mega-fighting types who I think have the best chance to break the core. Crobat would be ideal for these roles, since he can achieve that as well as adding poison and grass resists. Oh and a hazard user would help too :P