I forgot to mention that Calloway's also had lava sand and green sand. Might these be better for improving drainage?

Loam is a specific type of soil that consists of 45 percent sand, 25 percent clay, 25 percent silt, and about 5 percent organic matter. What is sold as "topsoil" is most often a mix of something the seller puts together and is most often a waste of your money purchasing since all you need do to your soil is add organic matter to create a soil even better then you can buy, for less money.
What your soil might need can be determined by a close look and these tests can help determine that.
1) Structure. From that soil sample put enough of the rest to make a 4 inch level in a clear 1 quart jar, with a tight fitting lid. Fill that jar with water and replace the lid, tightly. Shake the jar vigorously and then let it stand for 24 hours. Your soil will settle out according to soil particle size and weight. A good loam will have about 1-3/4 inch (about 45%) of sand on the bottom. about 1 inch (about 25%) of silt next, about 1 inch (25%) of clay above that, and about 1/4 inch (about 5%) of organic matter on the top.

2. Drainage. Dig a hole 1 foot square and 1 foot deep and fill that with water. After that water drains away refill the hole with more water and time how long it takes that to drain away. Anything less than 2 hours and your soil drains too quickly and needs more organic matter to slow that drainage down. Anything over 6 hours and the soil drains too slowly and needs lots of organic matter to speed it up.

3) Tilth. Take a handful of your slightly damp soil and squeeze it tightly. When the pressure is released the soil should hold together in that clump, but when poked with a finger that clump should fall apart.

4) Smell. What does your soil smell like? A pleasant, rich earthy odor? Putrid, offensive, repugnant odor? The more organic matter in your soil the more active the soil bacteria will be and the nicer your soil will smell.

5) Life. How many earthworms per shovel full were there? 5 or more indicates a pretty healthy soil. Fewer than 5, according to the Natural Resources Conservation Service, indicates a soil that is not healthy.

Do you intend this soil for containers or is it for adding to existing soil outdoors? That makes a very big difference!

I suspect this may be a container gardening issue :-) If so, I'd direct you to the attached thread from the Container Gardening forum that explains how container soils work. The cactus mix may be more appropriate than anything else you propose but even that is not ideal. For long term success, I'd suggest the gritty mix or the last recipe listed in the beginning post. And as it takes around 5 years before rhodiola develops any significant medicinal qualities, a long term container situation seems to be in the cards :-)

I'm not sure how well the plant will do for you in Texas - depends on where you are and what kind of weather conditions you can offer, especially in winter. Growing it in a container will certainly increase your options with it, though.

Here is a link that might be useful: Container soils - all you need to know