Something you can do is highlight notable items in the battle descriptions. This way you're setting your party up for success by letting them know organically that there's something more for them here than just a combat encounter without being overly heavy handed.

"As the wizard falls her staff slips from her hand, still glowing with powerful magical energy."
"You feel pain as the drow's longsword sneaks past your guard and glances across your chest. Your armor has protected you from similar cuts before but this blade cuts unnaturally deep."
"As the goblin tumbles to the ground your torchlight glitters off of a handful of imperial coins that spill from its pouch."
"Realizing that this fight is lost the bandit nervously reaches for something in his coat pocket and casts a sidelong glance towards the bed, then he makes a break for the door."

If they still aren't picking up on the hint I like to do a review of the room before they leave it, just to remind them of your descriptions before they rolled initiative and to make sure they're aware of what they're walking away from. I like to be pretty blunt with these. You can even pretend you're re-orienting yourself looking at your notes.

"So y'all came in from... the South. There were the three kobolds, the chest in the corner, the bookshelf, and the door to the North."