"I have paddeld into Allagash lake many time through Johnson pond.
"I was told that you can access the lake from the other end some what close to the fire tower. Has any one done it? How is the road?"
Yes, there's a gated road. It runs approximately 2 1/3 miles from Round Pond into the south end of Allagash Lake. I don't recall a parking lot, but two or three vehicles can park without blocking the gate and parking spots can be found nearby.
The southern terminus of the road into the lake is at 46.253651,-69.564915. It can be clearly seen on Google, satellite map mode.
Check out this old topo map.
http://docs.unh.edu/ME/alll61se.jpg
The road marked as "TELEPHONE" from Round Pond to Allagash Lake is ROUGHLY the same route as the current road.
You don't "need" wheels but I suppose they'd come in handy for a two-mile carry. A lot of people use them.
Also, you might also consider putting in at the spot marked "BR 1058" (on the old topo map) west of the lake on Allagash Stream. Parking for two-three of vehicles is available there. In my experience, that's the easiest entry into the lake. You can drive right to the put-in. You might have to wade and drag in some spots, but at least it's not muddy or bushy (like Johnson Pond) or lengthy (like the road from Round Pond).