Check out some of the articles here, but in a nut shell, apart from the fact that customers who obtain sex for consideration (or who communicate for that purpose) are committing an offence:
1. It is an OFFENCE for EVERYONE to advertise sexual services.
2. It is an OFFENCE for EVERYONE to materially benefit from the sale of sexual services.
3. It is an OFFENCE if anyone communicates about sexual services near children (school, daycare or playground).
4. Sex workers are IMMUNE from prosecution for OFFENCES in points 1. and 2. above (but this doesn't necessarily mean that they can't be arrested or charged - perhaps for harassment purposes or to gain leverage in extracting info about clients?).
5. Sex workers are also IMMUNE from prosecution for aiding, or abetting and entrapping buyers.
Offering companionship is preferred than to explicitly offer sex ("money is for time and companionship - anything else that happens is between two consenting adults"), as easier to get your clients in trouble if not scare them away. I doubt mention of 'roses' will matter, since the law doesn't specify money, only 'consideration'. You may not find a 3rd party venue to advertise sex outright, unless it involves an online medium with their server and office domiciled in a foreign jurisdiction.
Barter transactions were discussed in another thread. A customer can't get around the offence of 'obtaining sexual services for consideration' by bartering.
Also, read the CHALLENGED thread which details the likelihood of surveillance and onus of proof for LE when it comes to phone communications including sex.
One more thing: If you profit as a partnering SP in a commercial enterprise that engages in the offer of sex, you may be committing an offence too.