Timing belt changed, won't start

The OP indicated in their comment that they didn't maintain timing in the process of replacing the timing belt.

Since the 2007 Accord V6 has an interference engine, attempting to crank the engine over with the timing off will result in mechanical damage, which would explain why it is running roughly.

quick tip if any one is doing their timing chain or belt. make sure you have a picture showing the tdc( top dead center), double check all the marks match exactly no error is tolerated here, the crank, exhaust cams, intake cams etc.

the tip is first throw the belt on the crank, then align the belt on the cam which ever is far away from the tensioner, then on the cam closer to the tensioner, mae sure you dont have any slack on the belt, have all the slack towards the tensioner this way you will reduce the chance of the belt jumping tooth.

after assembling the belt make sure there is no slack,rotate the crank it should rotate with out too much resitance and the belt should not be jumping.

On the Honda SOHC V6 engine when doing timing the mark on the crank sprocket should line up with a small arrow on the block @ 12 o'clock.

The bank 2 cam gear should have the cylinder 1 TDC mark lining up with the indent on the backing plate.

The bank 1 cam gear is pretty much the same as bank 2. It has an indent and a mark on the cam gear.

A good practice to get into is rotating the crankshaft by hand after you have installed the tensioner and pulled the pin.

From the comments though it seems like your gonna need a new set of valves.

after I did the timing belt on my sisters car (2000 honda accord v6) was also mentioned that after you replace the belt and add the tensioner like required. Once all said and done with the install of belt, water pump gasket and pump, to rotate the motor by hand (with ratchet and socket) 3 or 6 full revolutions on the crank and all timing marks should align back up to all marks on the motor housing. After i did all this, her car ran like a champ on the first time of doing the service. now i make it a rule of thumb that if you do timing belt or chain, to rotate the motor 6 full revolutions (because cams rotate 1/2 speed of crank) and all timing marks will align back up properly.