With all due respect, REWARD and ROUNDUP are completely different chemistries that have distinctly different modes-of-action.
As PondRX indicated, REWARD rapidly destroys "contacted" plant tissue - and ONLY the portions of the plant's tissue that it contacts, so thorough contact is absolutely required. ROUNDUP/RODEO/AQUAMASTER and other formulations of glyphosate are systemic herbicides (meaning that they're absorbed and translocated within the plant's vascular system). Glyphosate herbicides impact enzymes that are only found in plants, inhibiting their production of necessary amino acids, thus causing susceptable plants to essentially starve to death - rather slowly.
NAVIGATE and AQUA-KLEEN (Granular 2,4-D formulations) are state limited-use in Texas. Though they're a consideration, an applicators license is required to purchase these types of products in Texas.
SONAR is definitely effective on lilies, but isn't normally used for such unless there are other species that also need to be controlled (as with Mr. Runkle).
There are a few other products available for consideration. But, water-uses and the ultimate objectives certainly play a vital part of the product-selection process.

Kelly Duffie
Cypress, TX