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[CountryBoyJohn]

Here is a tweak to Slim's suggestion.  Use a roof flange to protect your opening rather than a box.  See attached picture.  It has worked great for me.  I have one here for my main lines coming in and one for my hot tub lines. 

[hondaracer2oo4]

I think the minimum bend radius on 1 inch pex is 10 inches. On 1 1/4 it is obviously going to be much less. I think you would be able to do that through the 4 inch if you did a 45 followed by a straight section followed by another 45 to get your 90 complete. I don't think you will ever get it to turn that 90 in that short of a distance but I could be wrong. Easy enough to figure it out with a dry mock up. Just get a 90 and 2 sections of straight and try to get the 1 1/4 through it. I think it will try to kink on you. When I plumbed mine I have a old field stone foundation that is wide underground, about 3 feet wide atleast and as all large rocks. It wasn't an option for me to go through that easily. I ended up drilling a 4 inch hole through my bulk head footing. It was tight to get the pex through that and then bent around to head down into the basement. My bulk head has a ramp instead of stairs. I built a subfloor over the ramp and ran the pipes between the ramp and the subfloor.